Cream of the Crop 21/Cream of the Crop 21 (Terry Blount) (October 1996).iso/comm/servu20c.zip/SERV-U.TXT

Text File | 1996-08-10 | 140KB | 2,921 lines

                         FTP Serv-U


                FTP-Server Daemon for WinSock


                         Version 2.0








                         ************
       The Serv-U Web site: All you ever wanted to know
          about Serv-U and always the latest version

                   HTTP://www.cat-soft.com
                         ************




                         Revision 3
                         August 1996
                  ⌐ 1995, 1996 Rob Beckers
                          Cat Soft


                         Disclaimer
                         ==========

I  know, itÆs not the nicest way to start off. So letÆs  just
get this part over with, OK?!

The  FTP  server  program Serv-U and  its  documentation  are
copyright Rob Beckers. It is distributed as shareware, giving
you  the  right  to try it for a period of 30  days.  If  you
intend  to  use Serv-U after the initial try-out period,  you
are obliged to pay the registration fee.

The next paragraph is a beautiful piece of prose. In just two
sentences it says it all. Alas, with all the sue-happy people
in  this world it is unfortunately necessary, so please  bear
with me.

This software is provided by the regents and contributors æas
isÆ and any express or implied warranties, including, but not
limited  to,  the  implied warranties of merchantability  and
fitness for a particular purpose are disclaimed.  In no event
shall  the regents or contributors be liable for any  direct,
indirect,  incidental, special, exemplary,  or  consequential
damages  (including,  but  not  limited  to,  procurement  of
substitute goods or services; loss of use, data, or  profits;
or business interruption) however caused and on any theory of
liability,  whether  in contract, strict liability,  or  tort
(including negligence or otherwise) arising in any way out of
the  use of this software, even if advised of the possibility
of such damage.
Contents


Introduction

1. Making It Work - Installation
  1.1 Installation
  1.2 Network  Installation
  1.3 Quick Setup
  1.4 De-installation
  1.5 Upgrading
  1.6 Known Bugs & Problems
  1.7 A Word to the Wise (but paranoid)

2. Using Serv-U - How To . . .
  2.1 How to Setup Your Server
  2.2 How to Add a User
  2.3 How to Change a User
  2.4 How to Use Access Rules
  2.5 How to Setup Anonymous Access
  2.6 How to Use Groups
  2.7 How to See Who is Logged In
  2.8 How to Kick a User Off the Server
  2.9 How to Setup Logging
  2.10 How to Use Sign-on and/or Sign-off Messages
  2.11 How to Setup User Specific Login Messages
  2.12 How to Use Directory Change Messages
  2.13 How to Use Links α la UNIX
  2.14 How to Limit Access by IP Number
  2.15 How to Print via FTP
  2.16 How to Execute Programs via FTP with Serv-U
  2.17 How to Use Serv-U with æSLIP/PPP EmulatorsÆ
  2.18 How to use Netscape to access Serv-U
  2.19 How  to  Let  the Whole World into Your  Server  (and
       Delete All Your Files)
  2.20 How to use multi-homed IP support

3. The Inner Workings
  3.1 Serv-U Internals
  3.2 The SERV-U.INI File
  3.3 Using External User Access Verification DLLs

4. Getting In Touch - Bugs & Registration
  4.1 Serv-U Mailing List and Conference
  4.2 Reporting Bugs
  4.3 Registering Serv-U
  4.4 Registration in the US
  4.5 Registration from Abroad

Registration Form Serv-U


Introduction
============

Thank you for giving this program a try!

With  Serv-U, your PC will be turned into a FTP server.  This
means  that  others  on  the computer network  that  you  are
connected to (Internet for most people) can access your PC to
copy, move, make, and delete files and directories, using the
FTP  protocol  (FTP = File Transfer Protocol). This  protocol
dictates standard ways of communication between computers, so
that  many  different  types  of computers,  using  different
operating systems and file formats, can exchange files.

Serv-U  is a æserverÆ program and/or daemon. The term  daemon
comes  from ancient Greek mythology. There, the Daemons  were
half-gods, acting as messengers between the people  on  earth
and  the gods. This FTP server acts, likewise, as a messenger
for file transfer between FTP clients and your computer. Once
started  it  sits in the background waiting for a  client  to
contact  it and after communications are established,  acting
out the clientÆs commands.

There  are  FTP  servers  (and clients)  for  many  different
systems. This particular program is meant for PCÆs running MS-
Windows  that  have  a WinSock version 1.1 compatible  TCP/IP
stack installed.

Why  use  this  program and not one of  the  many  other  FTP
servers that are available? For this I have to take you  back
in  time  a  little, to about two years ago. I needed  a  FTP
server to make some files available to others and tried out a
number  of  server programs. One simply didnÆt work.  Another
would  work,  but as soon as someone started  transferring  a
file from my PC it would lock up the whole machine until  the
transfer  was  complete. And then there was one  that  worked
fine,  but lacked all but the most basic security. So,  after
endless  frustration I decided to write my own,  figuring  it
couldnÆt be that hard. As usual things got a bit out of hand,
but  after  a  year and 11000 lines of C++ there was  version
1.0.  The  current  version, v2.0, was made  about  one  year
later, and consists of  over 18000 lines of code. I hope  you
like the result!

So what has this FTP server to offer?

     ╖ Available  in 16- and 32-bit versions for  Win3.1,
       WFW3.11, Win95, and NT.
     ╖ At  the time of this writing there were over  2500
       registered users of Serv-U, with many of those for multiple
       copies!
     ╖ Access for multiple clients at the same time. Access for
       æAnonymousÆ users. With the possibility to limit the number
       of clients at any given time, so your PC remains workable.
     ╖ Lots of security! On a directory and even file basis.
       Allowing different settings for each user, and by putting
       users into ægroupsÆ permitting easy maintenance for large
       numbers of users. ThereÆs even an option to allow or prohibit
       clients on the basis of their IP-number. Ideal if you want to
       let certain people roam around your computer, but you donÆt
       want the whole world knocking at your door (that is to say:
       they can knock, but they wonÆt get in).
     ╖ Lots of features, like configurable sign-on and sign-off
       messages, per user configurable login messages, directory
       change messages, and UNIX-style ælinksÆ.
     ╖ Serv-U lets you execute programs remotely though your
       FTP client.
     ╖ It allows transfer to or from ports, like PRN:, LPT1:,
       COM1:, and AUX:. This allows you to setup your PC as a print
       server by simply transferring the file to be printed to the
       desired  port! Since the ports are part of the regular
       security system, a user needs permission to transfer to/from
       a port, allowing you to control who can use it.
     ╖ A quite complete implementation of, and very strict
       adherence to the FTP standard (found in documents RFC 959 and
       RFC 1123). Supports the æpassiveÆ command PASV. This is
       needed by WWW browsers and proxy agents (something required
       when there is a æfirewallÆ) for FTP transfer. Another feature
       is that you can let æAnonymousÆ users always see the root
       directory (æ/Æ) as their login directory. This, again, is
       needed by some WWW browsers to make FTP transfers work.
     ╖ Support for the æresumeÆ command and multi-homed IP
       server sites.
     ╖ Support for external user access verification DLLs.
     ╖ Easy to setup and maintain. Everything is accessible
       through menus, and for automated maintenance the settings are
       stored in an .INI file of simple format.
     ╖ There is lots of logging! You can select how much to log
       and where (to screen and/or file). The logfile is of a
       standard format to make machine reading easy, in case you
       need to do that for accounting purposes.
     ╖ It is fast! The file transfer speed youÆll get will be
       very close to the maximum your TCP/IP stack is capable of
       (well, assuming your FTP client is at least as fast of
       course).
     ╖ Life-time free updates when registered (As long as Serv-
       U exists).
     ╖ Compared to the commercial implementations, Serv-U is
       dirt cheap: less than 0.014 per line of code!

If  you didnÆt register this program, then youÆre looking  at
the  try-out  version of Serv-U. When started for  the  first
time, itÆll let you choose between a fully functional program
or  a  somewhat  crippled one. The text during  startup  will
explain  these  options  clearly. If  you  choose  the  fully
functional  version  then there is absolutely  no  difference
with  the  registered version. But (yes, there had  to  be  a
æbutÆ),  after  a little over 30 days it will  stop  working.
Counting  starts the first time you run the program.  I  warn
you beforehand: re-installing it will not help you!

Before I forget it: A big æThanksÆ to all the beta testers of
Serv-U.  The list is now so long it is no longer possible  to
mention each one individually, but you guys definitely helped
to  make Serv-U a better product! Any bugs that remain are of
course  my  own fault. Special thanks to Ryan and Kevin,  for
revising  the  manual! And, Alun, just after recovering  from
the  initial  shock of Serv-UÆs appearance, I hope  I  didnÆt
shock  you  again by bringing out a 32-bit version of  Serv-U
(There goes the monopoly). . .

OK,  enough  sales  talk.  LetÆs  continue  with  the  actual
documentation. First thing will be how to install  Serv-U  to
get you in business.


1. Making It Work - Installation
================================

YouÆre eager to get things going, but a little afraid of what
lies ahead. Never fear, it couldnÆt be simpler. So letÆs  get
started!

1.1 Installation
----------------

Nothing is simpler than installing Serv-U: just unzip  it  in
the directory of your choice and run it. There is no need  to
change your æPATHÆ or put anything in other directories.

The Serv-U zip-file comes with the following files:

     SERV-U16.EXE    - The 16-bit version of the  FTP-server
                       executable itself
      - and/or -
     SERV-U32.EXE    - The 32-bit version of the  FTP-server
                       executable
     SERV-U.DOC      - The  documentation  in  MS-Word
                       version 6.0 format
     SERV-U.TXT      - The documentation in ASCII format
     README.TXT      - Something you have to read
     REGISTER.TXT    - A registration form in ASCII format
     VERSION.TXT     - A list of changes between the  various
                       versions.
     FILE_ID.DIZ     - Short description file for use by
                       bulletin boards

When  Serv-U  is started for the first time, it  creates  the
file:

      SERV-U.INI     - File containing all settings  and
                       user information

The 16-bit version of Serv-U uses MicrosoftÆs 3D-controls  to
make the dialogboxes look better. If for some reason you  get
flat-looking  dialogboxes it means that the file  CTL3DV2.DLL
is  missing.  This  file should be in your WindowÆs  æsystemÆ
directory.  It  is rare if this file is missing,  since  just
about  anything these days uses it. However, if  you  need  a
copy then drop me a line. The 32-bit version uses Windows  95
style controls. This means things will look flat on NT,  this
is normal. In Win95 you will automagically get the 3D-look.

Serv-U offers two very distinct ways to try it out. Each with
its  own  advantages and disadvantages. When started for  the
first time (or in absence of a SERV-U.INI file), it will show
you  a screen explaining the two try-out options and allowing
you  to  choose  one  of them. The first choice  is  a  fully
functional  try-out version exactly equal to the real  thing,
but it will stop working after 30 and some days. It does this
by  contacting  a permission server over the  Internet  every
time Serv-U is started. The permission server keeps track  of
when the program was started for the first time and uses that
information  to  determine if it should  be  allowed  to  run
again,  or not. It then sends this answer back to Serv-U  and
the program will consequently work or stop. To this effect, a
network packet is sent to the permission server containing  a
version code, the IP number of your PC, and a run/norun flag.
It  receives back the same packet with the flag set to run or
stop.  This is all that is communicated between the  systems,
nothing more, nothing less!

The  second  choice  is a try-out version  that  is  somewhat
crippled. It will only allow a total of 10 file transfers  (5
PUTs  and  5 GETs), it will show a message saying it  is  not
registered  to anyone who logs into the server, and  finally,
it  will  only stay on-line for one hour. You have to restart
it  again  after that to get another hour. The  advantage  is
that  it  will  not  contact my permission  server  over  the
network.

Just to make sure this is clear: Once Serv-U is registered it
will NEVER send anything over the network other than what  is
needed  for  regular  FTP traffic! In short:  The  registered
program will NOT contact my permission server!

1.2 Network  Installation
-------------------------

To  find  the  setup information, Serv-U first looks  in  the
program directory (i.e. where SERV-U.EXE is located) for  the
file  SERV-U.INI. If no .INI file is found, the program looks
for  the  existence of an environment variable with the  name
SERV-U. If this variable exists, it should be set to the path
for  SERV-U.INI. The program will then use the .INI file this
path  points  to.  For network use with a  single  executable
shared  between many users that need their own settings  this
is  a  convenient  way to set things up. If this  environment
variable  does  not  exist, the whole DOS  path  is  searched
including  the  Windows directories. If a file SERV-U.INI  is
found somewhere it will be used, this way also allowing for a
single  copy  of  the  executable on a network  server  while
having  individual settings for each user. Finally, if  SERV-
U.INI  was still not found, it will be created in the default
program directory.

If  a  SERV-U.INI file is available it does not  have  to  be
writable  per se. The program will work when it is read-only,
but  setup  changes and the current position  of  the  Serv-U
window will not be saved.

1.3 Quick Setup
---------------

When you run Serv-U for the first time there will be no users
and  access  will be restricted.  This section will  describe
the  bare  necessities to allow access. In addition  you  can
also  go  through  the æSetupÆ menu items  and  put  in  your
heartÆs  desires. The next chapter will explain  the  various
options and how to use them. You might want to take a look at
it,  since  the  setup  is simple but not  totally  intuitive
(Sorry for that, I tried hard but . . .).

Now, to quickly get Serv-U up & running, just start it. Leave
all  the settings at their defaults, since in most cases that
will be OK. Right!

At  this  point you have a functioning server but no  defined
users,  so  no  one can log in. To define users,  go  to  the
æSetup  - UsersÆ section  in the menu and youÆll see a  blank
user  setup  screen. Now IÆll assume you want to  setup  your
server  for  anonymous  access. To make  that  work,  do  the
following:

     ╖ At  æUser  nameÆ, type the name we  want  to  add:
       æanonymousÆ
     ╖ At æHome directoryÆ, type the directory where you want
       anonymous  users to be. LetÆs assume we want  them  on
       æd:\anonftpÆ, so enter this (or press æBrowseÆ and choose
       your favorite home directory for anonymous users).
     ╖ Press the æAddÆ button of the æFile/Directory access
       rulesÆ section.
     ╖ Anonymous users need access to their home directory, so
       enter æd:\anonftpÆ in the dialogbox and press æOKÆ.
     ╖ ThatÆs all, just leave the other settings at their
       default values and press æStoreÆ to save your setup.

You  now have a user with name æAnonymousÆ that can log  into
the  server.  Of  course, if you want anonymous  users  in  a
different  directory then æd:\anonftpÆ,  then  feel  free  to
change  this. Just make sure that the directory  you  specify
actually exist and that it is part of the access rules.

If  the  zip-file you have came with both the 16- and  32-bit
version    of    Serv-U   (SERV-U16.EXE   and    SERV-U32.EXE
respectively), and you only need one of them, then you can of
course delete the other to free up disk space.

1.4 De-installation
-------------------

It  is  hard to imagine why, but if for some reason some  day
you  want to get rid of Serv-U then that is just as  easy  as
was  installing it. Just delete the whole directory where you
put  it,  and  thatÆs it! Serv-U does not change  any  system
files and does not place any files in other directories.

1.5 Upgrading
-------------

Upgrading from an earlier version of Serv-U is not difficult,
but  there are a few things to keep an eye on. Here  are  the
steps to follow:

     ╖ If you are running Serv-U: Exit the program.
     ╖ Make a backup of the old Serv-U files. Just in case. . .
     ╖ Unzip the new Serv-U zip-file in a temporary directory
       and copy the contents over the existing files in your Serv-U
       directory (Watch out that you get the direction of copying
       right!).
     ╖ Go to the Serv-U directory and delete the file BWCC.DLL
       if it exists, version 2 no longer needs this file. Note: Only
       delete BWCC.DLL if it is in the Serv-U directory, do not
       delete the one in the Windows\System directory as other
       programs might use this.
     ╖ If you are using signon or signoff messages with æ%Æ
       directives, then you will have to change those. The old
       directives no longer work. Take a look at the æHow to setup
       sign-on and/or sign-off messagesÆ section for the  new
       directives.

Your  old SERV-U.INI file will be used by the new program  so
you donÆt have to re-install any users.

The 16-bit version of Serv-U now uses MicrosoftÆs 3D-controls
to create a 3D-look. This is done by a file named CTL3DV2.DLL
which should be in your WINDOWS\SYSTEM directory. Most likely
you  already have this file, and therefore it is not part  of
the  Serv-U zip-file. But if the dialogboxes look  flat  then
drop  me a line and I will make the DLL available. Note  that
this is only meant for the 16-bit version of Serv-U. The  32-
bit  version will always look flat on NT (Until NT adopts the
Win95  look)! On Windows 95 the 32-bit version will  use  the
built-in 3D-controls, and thus have a 3D-look.

1.6 Known Bugs & Problems
-------------------------

At  the  time  this documentation is being written  the  only
known  bug  left in the program is the lack of on-line  help.
Everything that was found in earlier versions has been fixed.
If  you  have  any  problems,  please  first  check  out  the
æFrequently  Asked QuestionsÆ on my Web site (HTTP://www.cat-
soft.com).  I will do my best to keep an up-to-date  list  of
everything worthwhile there.

Unfortunately  there  are still a number  of  WinSock  socket
stacks that are not 100% compliant with the WinSock standard.
Since  Serv-U uses the stack to its fullest, this can  result
in  a  number  of symptoms. The following has been  observed:
directory listings and file transfers do not work; after  the
first  client  the  server seems blocked; WWW  browsers  seem
unable to work with Serv-U; the PC is blocked when Serv-U  is
transferring a file.

Problem WinSock socket stacks
-----------------------------
Below is the current list of socket stacks that are known  to
cause  problems.  If you find any others  with  problems,  or
solutions to the ones mentioned below, please let me know  so
I can pass the word on to others.

     ╖ FTP Software Inc's socket stack: Their earlier stacks
       cause problems. Version 2.2 with WINSOCK.DLL v1.15.1 is
       rumored      to      work      OK.      Check      out
       ftp://ftp.ftp.com/support/ftpsoft/winsock for updates. Their
       latest version WINSOCK.DLL can be found in WINSOCK.EXE
       (currently v1.17.1).
     ╖ Spry's Internet-in-a-box stack: Version 2.0 is rumored
       to          work         OK.         Check         out
       http://www.spry.com:80/products/upgradingibox.html for
       updates.
     ╖ The Air socket stack is rumored to come from the same
       factory as SpryÆs. WonÆt work though.
     ╖ Core Systems' Internet-Connect stack does not work with
       Serv-U.
     ╖ DEC's PathWorks stack does not work either.
     ╖ Sun's PC-NFS stack version 5.1A and later works, but
       earlier versions are a problem.
     ╖ Earlier versions of the Microsoft Wolverine stack had a
       tendency to bomb back to DOS when the network got busy. This
       has  been  fixed  in  version  3.11b,  available  from
       ftp://ftp.microsoft.com/bussys/clients/wfw/tcp32b.exe. A
       highly recommended stack!
     ╖ Novell's LanWorkplace stack seems to work for some
       people, but doesn't for others. In any event, you need
       version 4.2T3 or later. The 'T3' patch is available from
       http://netwire.novell.com/servsup/binhtml/1203536.htm.
     ╖ In case you have Netmanage's Chameleon's Sampler you
       need at least version 3.11. Reports are that it works fine on
       version 4.5.1 of Chameleon.
     ╖ PC/TCP's OnNet stack locks up the PC during file
       transfers, but it works fine otherwise.
     ╖ CompuServe's WinSock stack does not work with Serv-U
       (WasnÆt that bought from Spry?!).
     ╖ The  various  versions of Trumpet's WinSock  stack
       generally work fine. But, version 2.0b had a tendency to kill
       the socket Serv-U uses to listen for incoming clients, thus
       making the server unreachable. This has been fixed in version
       2.1f,     so     better    get    that    one     from
       ftp://jazz.trumpet.com.au/pub/winsock/twsk21f.zip.
     ╖ QuarterdeckÆs socket stack does not work with Serv-U.
     ╖ The Windows 95 built-in 16-bit TCP/IP stack usually
       works fine, and is very stable. But, it sometimes kills Serv-
       UÆs listening socket, resulting in æConnection deniedÆ
       messages  from clients. This is a Win95 bug  which  MS
       acknowledges and claims to be the result of programs not
       freeing their sockets before terminating. The latter is
       probably BS, IMHO, but it lets them pass the buck. Most
       people will never see this while others seem to have the
       problem continuously.

æSLIP/PPP emulators - TIA, TWinsock, PipelineÆ
----------------------------------------------
If  you  are  using  a  so called 'SLIP emulator'  like  TIA,
TWinsock,  or Pipeline, there are also a number of things  to
keep   in   mind.  These  emulators  are  not  real  Internet
connections,  and because of the way they have  to  do  their
work they have a number of peculiarities. Since the PC has to
share  the  IP number with the host system you will generally
not  be  able to use the default port 21 for Serv-U. Instead,
you  either  have to use a high port number (generally  above
8000) or set up 'port redirection'. Ask you Internet provider
for  details about the latter. A related problem is that  the
IP  number  displayed by Serv-U is not  the  IP  number  that
clients  should use to contact your server. It  is  merely  a
dummy  to  keep  the socket stack of the PC  happy.  For  the
outside  world the IP number of your server is  the  same  as
that  of the emulator host system, i.e. that of your Internet
provider. Another special effect is that clients will not  be
able  to  use 'passive' mode for data transfers.  This  means
that  regular FTP clients will work OK, but WWW browsers like
Netscape and Mosaic will not work when Serv-U runs via a SLIP
emulator.  For  the same reason it won't be possible  to  use
clients that are also connected via a SLIP emulator.

Dynamic IP
----------
If  you  use a modem and telephone to connect to the Internet
via a service provider, then chances are that you will get  a
different IP number each time you connect to the network. You
can  see  what  your current IP number is by looking  at  the
startup  messages  of  Serv-U: one of the  lines  is  the  IP
number. Serv-U does not have a problem with dynamic IP.  Just
make  sure  you  start the server after  connecting  to  your
service  provider,  so  Serv-U will  report  the  current  IP
number.  However, if you want to run a steady FTP site,  then
dynamic  IP  is a pain in the lower rear end! You users  will
have  to  know  which IP number to contact and  if  yours  is
changing all the time it does not help. . .

Your  IP number is entirely up to your provider and there  is
absolutely nothing Serv-U can do about it! It merely uses the
number  available.  So,  if you want a  fixed  (æstaticÆ)  IP
number  the  only person to talk to is your Internet  service
provider. Sometimes it is possible to get a fixed symbolic IP
name, even though the number varies each time (An IP name  is
something like æwww.cat-soft.comÆ, you can use it instead  of
an IP number). Again, talk to your provider.

1.7 A Word to the Wise (but paranoid)
-------------------------------------

Many  a  word has been spent on the alt.winsock newsgroup  on
the  try-out enforcement practice of Serv-U, and in a broader
sense on the security of network programs. If you choose  for
the æfully functional try-out versionÆ then this program will
communicate with a remote system to determine if it should be
allowed to run or not. That is the way the 30 days of try-out
are  enforced.  To  that  effect,  information  is  exchanged
between your PC and mine, and as people asked: How do I  know
that  my  password file is not being sent over? Another,  but
similar  question is: How can I be sure there  are  no  æback
doorsÆ  in the server, allowing access to the author  at  any
time?  The short and hard answer is: You donÆt know  and  you
can never be sure!

I  know this is not much of a deal, so IÆll at least give you
one option to establish my good intentions. To anyone who  is
interested,  I  offer to personally go over the  source  code
with you (all 18000+ lines of it) and weÆll compile it on the
spot. You will understand that I am not going to hand out any
source  code. If you want to take it home youÆd better  bring
along a whole lot of $$$Æs!

It  is worthwhile to realize that security is a problem  with
any  type  of  network  program. It  is  fairly  easy  for  a
programmer  to put code in, for example, a WWW  browser  that
will  wait  for  5  months, until the  full  moon  and  Venus
coincide, then monitor PC activity and if a user hasnÆt  been
present for a few hours, or if itÆs 4 in the morning,  starts
sending  over  the  whole hard disk to unknown  destinations.
This  kind  of thing is not easy to detect, donÆt let  anyone
tell  you  otherwise, and I still have  to  meet  the  system
manager that keeps a network monitor running 24 hours a  day,
year  after year and actually reads the log files. The bottom
line  is  that you will have to trust the author of a program
at some point, there is no other choice!

Now donÆt write to me that conversely I should trust you that
"the check is in the mail and please send me the registration
key in advance". . .

That  is all I have to say about installing Serv-U. Now letÆs
look  into how we can use it to get some real work done.  The
next chapter will take you through all its features.


2. Using Serv-U - How To . . .
==============================

Rather  than describing every menu and dialogbox to its  last
boring detail, I though it would be more useful to present  a
task-driven approach. This chapter is therefore divided  into
sections that each describe how a specific task can be  done,
in the form of æHow toÆ questions and answers. There is a bit
of overlap between the sections, so you might come across the
same  thing more than once. If you read this manual cover-to-
cover  then you will also have learned about every  menu  and
dialogbox  detail  in  the  process.  Makes  great   bed-time
reading!

2.1 How to Setup Your Server
----------------------------

You  shouldnÆt believe all I say: This first section is going
to  go  over  the æSetup - FTP ServerÆ menu choice  in  every
grueling detail! No, seriously, this dialogbox stands so much
at  the basis of Serv-UÆs operation and the items in there do
not  fit very well in other sections, that it is a good  idea
to  cover it first, and I will only discuss those items  that
are  not  covered by other sections. So, letÆs  pull  up  the
æSetup FTP-ServerÆ dialogbox.

The first item is æFTP port numberÆ. This is the (you guessed
it!)  port number that the server will listen on for incoming
FTP  clients.  The default is number 21, but youÆre  free  to
fill in anything you want, provided it does not conflict with
other  network  programs. Of course, the rest  of  the  world
expects  a  FTP server to listen on port 21, but changing  to
another number is one great way of insuring that only you and
some selected friends will know about your server.

The  next  item is the æMaximum no. of usersÆ. With this  you
set  the  maximum number of simultaneous users at  any  given
moment.  Setting  it  to 0 will not allow  anyone  to  enter,
leaving  it  blank will allow an unlimited number,  or,  more
precisely, until the PC runs out of network sockets or  other
resources  like memory. If you need your PC for regular  work
as  well as being a FTP server, it is probably wise to set  a
maximum so normal operations will not be slowed down too much
by  clients. Likewise, æMaximum no. of anonymousÆ limits  the
number  of æAnonymousÆ users at any given moment. If æMaximum
no.  of  usersÆ is specified, then this will limit the  total
number of users, both regular and anonymous, even if æMaximum
number of anonymousÆ is set to a larger number.

Some people have asked what would be reasonable settings  for
the  maximum number of users that would still keep the system
workable. The answer is: It depends. It depends very much  on
whether these users are local and thus capable of using up  a
large  bandwidth in data transfer, or alternatively, if these
users  are  further  away  on the  Internet  and  cannot  get
transfer  speeds  of  more than about 10 Kbytes  per  second.
Another  concern  is  the socket stack. Some  WinSock  stacks
start  behaving erratically when they have to  service  large
numbers  of  sockets. Most notoriously is or  was  the  first
version of the Microsoft 32-bit æWolverineÆ stack, which  had
the  tendency to kick the system back to MS-DOS  without  any
warning  when  heavily loaded. One way to find out  how  many
users  your system can handle, in case you run Windows 95  or
NT, is to start the system monitor and keep an eye on the CPU
usage percentage. This will give you a pretty good idea  very
fast.  My experience is that even a measly 486 can handle  20
or so concurrent users with easy.

This  brings  me  to another topic which is  related  to  the
above:  Server stability is going to depend very much on  the
operating  system you are using. MS-Windows 3.1  and  WFW3.11
are  inherently so unstable that you should not expect Serv-U
to  run for more than a few days at a time before a reboot is
needed. Very much better is Windows 95, especially when  used
with  the  build-in socket stack. Having used  it  since  the
early  betas  it seems to work fine for several  weeks  at  a
time. Definitely recommended for serious server work! At  the
top  of  the  stability  list stands NT.  I  donÆt  have  any
experience with it myself, but people using Serv-U in NT tell
me it is very stable.

Another often asked question concerns maximum transfer speeds
that can be obtained with Serv-U: LetÆs just say that even on
a  measly  486 you donÆt have to worry about this unless  you
have  at  least  a T3 network connection, Serv-U  can  easily
saturate  a T1 line (= about 1.5 Mbits per second).  You  can
try  out raw speed by yourself: Just start a FTP client, like
WS_FTP  on  the  same PC as where the server is  running  and
transfer some files through it. This bypasses the network, so
what  you are seeing is Serv-U plus hard disk access and part
of  the  socket stack. The conclusion from this will probably
be  that your biggest performance bottle neck is going to  be
your network connection.

LetÆs  get on with the list. To  make sure that users  cannot
log onto your server and keep connections open until eternity
it   is  possible  to  set  æTime-out  usersÆ  and  æTime-out
anonymousÆ. If a connection has been idle for more  than  the
number  of  minutes you specify here it will be automatically
closed.  Filling  in 0 or leaving it blank switches  off  the
time-out.  It  is  a good idea to fill in some  values  here,
since  otherwise the system would slowly fill up with sockets
that  for  some reason got stuck, not to mention  users  that
connect  and  start  a transfer just before  they  leave  the
office in the evening and then go home. Default values are 15
minutes  for anonymous users and 10 hours (=600 minutes)  for
regular users.

If  you would like to leave your PC wide open for the rest of
the world you can uncheck the æEnable securityÆ checkbox. But
beware:  DISABLING SECURITY WILL ALLOW ANYBODY ON THE NETWORK
TO  DELETE/CHANGE/COPY  EVERYTHING ON  YOUR  PC!!!  The  only
reason  I  put this option in is to make it easy  for  people
that have their own local network and donÆt want to mess with
users  and  passwords. By default this option is, of  course,
checked.  DO  NOT  EVER  LEAVE THE æEnable  SecurityÆ  OPTION
UNCHECKED IF YOUR PC IS CONNECTED TO THE INTERNET!!!

2.2 How to Add a User
---------------------

One of the most fundamental tasks you are going to have to do
is  adding  new users. Unless you switched off all  security,
you are going to have to deal with this.

Upon choosing the æSetup - UsersÆ menu option a dialogbox  is
presented  to you. It contains a list of all known  users  on
the  left and by clicking on one of those users you  can  see
the  settings for that user on the right side.  Now,  if  you
just started this server for the first time there will be  no
names  in the list, short of Divine Intervention. If you  are
at this point and are about to setup your first user, just go
ahead  and  type in the various fields. If there already  are
users defined you will see the settings of the first one  and
to  get  rid  of  this and create an empty sheet  just  press
æNewÆ.  Doing the latter will pop up a little box asking  you
for the new userÆs name, which I think speaks for itself.

The  next thing is important, so pay attention: You can  fill
in  or change any name in the æUser nameÆ field. If this  new
name does not exist it will be added to the list of users. If
this  name exists, the settings for this user will be changed
to  the ones in the dialogbox. In short, this is another  way
to add new users. So, if you clicked on user æJamesÆ and then
go  on to set his password to ælightbulbÆ and you change  the
user  name  to something that does not exist yet,  letÆs  say
æTanyaÆ, then you just created a new user Tanya with all  the
settings  of  James  except for his  password.  This  way  of
dealing with users might strike you as somewhat strange.  The
advantage of it is that you can take an existing user and, by
making only the few needed changes, turn it into a new user.

Now  letÆs  take a closer look at the various fields  in  the
æSetup  UsersÆ  dialogbox. IÆve dealt with  the  æUser  nameÆ
field,  so this brings us to æGroup nameÆ. Every user can  be
part  of a group. The convenience in making users part  of  a
group is that you can leave common settings for all users  of
a particular group blank and just fill them out in the æSetup
GroupÆ  dialogbox, about which you can find more  information
later  on  in the æHow to use groupsÆ section. This goes  for
all  settings,  including password, home directory  and  path
access  rules.  To overrule a certain group  setting,  simply
provide  one for the user. Only exception for groups  is  the
user  with  special  name æAnonymousÆ.  For  æAnonymousÆ  the
system ignores any group setting you might have. In fact,  if
you  try to enter a group for a user with that name it  wonÆt
even  get  stored and is gone the next time you look  at  the
settings for æAnonymousÆ.

We  did  get  ahead  of ourselves in the  discussion  of  the
various fields, so let me back up a bit. The æPasswordÆ field
is  of course for adding a password for a user. The passwords
are stored encrypted using UNIX æcryptÆ. This algorithm works
like a sausage machine: you put in a pig on one side and turn
the crank, out comes the sausage. But, pushing in the sausage
while turning the crank backwards will not get you a pig!  It
is  quite  secure, I wouldnÆt know of a way to get the  plain
text password back (the NSA might though). Once a password is
stored  you  will  only see the word æ<<Encrypted>>Æ  in  the
password field. This is to indicate there is a password.  You
cannot  edit existing passwords, since the original is  truly
lost  and  only the encrypted form is kept. The only  way  to
change it is by typing in a completely new one.

If you leave the password field empty this does not mean that
the  user has no password. Serv-U assumes that all users need
a  password and will try if there is a group setting and look
there  for  the  password. If no password can be  found  then
access will be denied to the user. There is a way to setup  a
user without a password, but  it needs direct editing of  the
SERV-U.INI  file. You can find the details in the chapter  on
Serv-U internals.

There  is  one  more  exception  with  passwords  that  youÆd
probably already know: The user name æAnonymousÆ never has  a
password. Instead, Serv-U will ask for a E-mail address.

The  æHome  directoryÆ field is for the userÆs home directory
(To  kick in an open door). This is the place where he or she
is  put immediately after logging in. Each user needs a  home
directory, without one the server will not permit logging in!
Of course, if a user is part of a group, and this group has a
home  directory you donÆt have to specify one here. You might
want to, if this user needs a different one from the rest  of
the  group.  Home  directories always need to  be  full  path
names, including a drive letter!

This  brings us to the æMessage fileÆ field. You  can  put  a
file  name of a text file in there. The contents of this file
will  be  displayed to the user just after logging  in.  More
about this in æHow to setup user specific login messagesÆ. If
you  want  the  user  to be able to actually  use  the  newly
created  account, then the æEnable accountÆ check box  should
be  kept  checked. If you want to disable the account without
removing  the  setup information of a user  you  can  uncheck
this, which will keep the user from logging in.

A  large portion of the æSetup UsersÆ dialogbox is devoted to
æaccess   rulesÆ.   These  determine  to  which   files   and
directories a user has access. In general, you will  have  to
make  sure that the user has at least read access to  his  or
her  home directory. The quick-and-dirty way to setup  access
for a user is therefore to press æAddÆ and enter the path  of
the  userÆs home directory. Then check the appropriate access
rights, which in this case should be at least æreadÆ, ælistÆ,
and  æinheritÆ,  and you have a functional account.  Although
their use is pretty straight forward in most cases there  are
still  some  ins and outs to access rules. So please  take  a
look at the section æHow to use access rulesÆ which discusses
them in more detail.

Obviously, clicking the æStoreÆ button will store  the  newly
created user settings. But this is not the only way: You  can
also  leave  the setup screen by pressing æOKÆ,  any  unsaved
changes  will  be stored as well. Also, if you  already  have
other  users set up, clicking the mouse on another user  name
will save changes.

We  already came across the special user name æAnonymousÆ  to
allow  access  without a password. The  user  name  æFTPÆ  is
understood  by  Serv-U as a synonym for æAnonymousÆ.  When  a
user  enters  æFTPÆ it will be translated to æAnonymousÆ,  so
the  latterÆs settings apply to æFTPÆ. There is one more user
name  with  special meaning to Serv-U: æALLÆ. Now where  does
this  tie in? Well, every action requiring security clearance
(checking a password during login, reading, writing, etc.) is
first  checked against the settings for the particular  user.
If  no  appropriate  setting is found  there,  and  the  user
belongs  to  some group, the group settings are  checked.  If
still  no  corresponding setting is found, the user æALLÆ  is
consulted (if it exists). So æALLÆ works as a blanket for all
users,  providing the most common settings. Of  course,  this
also provides a potentially big security hole, so be careful!

This  should  have you started in creating user account.  The
next  section  gives  you  a few details  on  how  to  change
existing user accounts.

2.3 How to Change a User
------------------------

For  the  most  part  the things mentioned  in  the  previous
section,  æHow  to add a userÆ, also apply to  changing  user
settings. However, there are a few peculiarities that deserve
extra attention.

First  of  all,  keep in mind that you can  change  a  userÆs
settings  at  all times in the æSetup UsersÆ dialogbox.  This
includes  the userÆs name, but care should be taken in  doing
this,  since there might be side effects: If you  change  the
name  to a non-existent one and store the settings this  will
in  effect  create a new user with that name.  Also,  if  you
change  the  name  to one that already exists  then  you  are
changing  the settings for the user with that name!  To  drag
our  favorite example once more out of the closet: LetÆs  say
you  want  to  change the password of user  æJamesÆ.  So  you
clicked  on  æJamesÆ and then go on to set  his  password  to
ælightbulbÆ and you change the user name to that  of  another
user,  letÆs  say æTanyaÆ. Then Tanya is going to  be  mighty
upset when she tries to enter your FTP server! James will  of
course  have  to  remember  his old password,  since  nothing
changed for him.

Another peculiarity that can come in handy is when changes to
user  settings get stored. There are several ways to do this.
Obviously clicking on æStoreÆ will do the trick. Another  way
is to press æOKÆ and leave the user setup. This will save any
changes  too. The third and last way to store changes  is  by
simply  selecting another user from the list on the  left  of
the  æSetup UsersÆ dialogbox. Up until you store changes  you
can  recover  the  original  settings  by  the  pressing  the
æRestoreÆ button. This does not hold for the æDeleteÆ button.
Pressing  this  will erase the selected user  completely  and
there is no way to get it back (IÆm a nice guy, so youÆll get
warned first when attempting this)!

If  youÆre  editing an existing user who has a password,  the
word  æ<<Encrypted>>Æ will be shown in  the  password  field.
This  indicates there is a password, as opposed to not having
a  password in which case this can be supplied by  the  group
settings.  There is no way to recover the original  password,
once  entered it is lost! So, there is no possibility to edit
the  existing  password, you can only enter a completely  new
one.  To  do  this, erase the word æ<<Encrypted>>Æ completely
and type in the new password.

Something that might be of interest to you if you edit  users
by  directly changing the SERV-U.INI file using your favorite
text editor (for example ænotepadÆ): Any changes you make  to
users  take immediate effect. No restarting of the server  is
needed.  This means that you could keep a local copy of  your
INI  file and use a local version of Serv-U to edit it.  Then
just  use  Serv-U itself for uploading the changed SERV-U.INI
file to the production site and you are all set.

That  concludes all you need to know for keeping your  userÆs
settings  up-to-date, but it is time to fill in a  big  blank
that is of the essence to using Serv-U: The access rules.

2.4 How to Use Access Rules
---------------------------

The  æAccess rulesÆ part in the æSetup UsersÆ dialogbox forms
the  corner stone of Serv-UÆs security. This is also the part
that  makes  Serv-U unique: It allows very fine control  over
what   a  user  can or cannot do. It allows  you  to  specify
access per directory and even per file for each user!

How  does  all  this work? Take a look at the æFile/Directory
access rulesÆ list in the æSetup UsersÆ dialogbox. This  list
contains a number of paths with access information coupled to
each  path.  Access  to the PC is only allowed  according  to
these paths and their access information. No access path,  no
access! So, there is one path you might always want to be  in
the  list: The userÆs home directory. The check boxes at  the
right of the path list show what kind of access the user  has
to  the path in the list. Again, unless the type of access is
specified in these check boxes the user wonÆt get in.

LetÆs  take  a  look at the different type of access  we  can
specify  per  directory or file. There  are  eight  different
types  of access information that can be set, four that apply
to  files,  three for directories, and the  final  one  is  a
special case. To start with file access:
     ╖ æReadÆ  access, allows files to be copied from  the  PC
       using the FTP ægetÆ command.
     ╖ æWriteÆ  access, allows files to be copied  to  the  PC
       using æputÆ, but not changed, deleted, or renamed.
     ╖ æDeleteÆ access, allows the user to change  files,
       rename, or delete them. Having æDeleteÆ access automatically
       includes write access (although it does no harm to specify
       both).
     ╖ æExecuteÆ access, is meant for executing files through
       FTP, i.e. for running DOS and Windows programs remotely.

Then there are three items that deal with directories:
     ╖ æListÆ access, allows the user to retrieve a directory
       listing using the FTP ædirÆ command.
     ╖ æMakeÆ access lets the user create new directories at
       this path, i.e. the user can make subdirectories.
     ╖ æRemoveÆ allows the user to delete directories.

The final item is somewhat special:
     ╖ æInheritÆ means that the access rule automatically
       applies to all subdirectories of the path, i.e. the rule is
       inherited by subdirectories.

Most  of  the above should be no surprise to you,  but  letÆs
take  a  closer look at a few of the less clear items. First,
to  allow  a user to use the FTP command æcdÆ to get  into  a
directory  any of the rights is sufficient. So, a  user  that
has æreadÆ, æwriteÆ, ædeleteÆ, æexecuteÆ, ælistÆ, æmakeÆ,  or
æremoveÆ  can  change to the directory in  the  access  path.
Conversely, if a path is specified without any access  rights
(except  for æInheritÆ) then the user has no access  what-so-
ever to this path.

A  user has æwriteÆ access to a file or path, but no ædeleteÆ
access, can upload files to the server as long as they do not
exist  already. This is good for an upload directory, because
it  allows  uploads without the chance of changing previously
uploaded files.

æExecuteÆ access is meant for remotely starting programs  and
usually  applies  to specific files. Be careful  in  granting
this right: For example, allowing a user to start COMMAND.COM
also  means that this user can delete anything on  your  hard
disk! More on using this in the æHow to execute programs  via
FTP with Serv-UÆ section.

If  you want a user to be able to see a directory listing you
need  to  specify ælistÆ access. This is often  used  in  the
opposite  way: For example for an upload directory you  would
want  a  user  to be able to upload files, but  not  see  and
certainly  not download anything that is already there.  This
could  be  done  by  only specifying the æwriteÆ  right,  and
leaving ælistÆ access unchecked.

A  somewhat strange attribute in the list is æinheritÆ.  This
does  not  so much say anything about access for a path,  but
how that access rule works for subdirectories. When æinheritÆ
is  checked  the  rule will automatically be  valid  for  all
subdirectories  of  the  path  in  the  rule,  as  if   these
subdirectories  inherit  the access  rule.  This  is  usually
convenient, it means that with a single access rule  you  can
control access to a whole branch in the directory tree. Also,
if a user is allowed to create subdirectories, they will have
the same access rights as the parent if æinheritÆ is checked.
In short, you are going to want to leave æinheritÆ checked in
most  cases,  but sometimes it can be convenient  to  specify
access  for  a  single directory in a tree without  affecting
subdirectories  and thatÆs when unchecking  it  can  come  in
handy.

When  a  user  executes an FTP command  concerning  files  or
directories, the userÆs access path list is checked to see if
the  command should be allowed to proceed. Now pay very close
attention, this is the part of Serv-U that seems  to  be  the
least  understood: The list is evaluated from top to  bottom,
and  evaluation stops as soon as an applicable rule is found.
æApplicableÆ means that if it is a file the user wants to  do
something with, then the file name must appear in the  access
path  list, or the directory of the file must be in the list,
or  finally, a parent directory of the file must  be  in  the
path  list  with æinheritÆ checked. Directory access  uses  a
similar mechanism. It follows from this that THE ORDER OF THE
PATH ACCESS RULES IS IMPORTANT!!! Unless the access rules are
in the right order you will not get the result you want!

Since  one  example  can say more than a thousand  words,  or
something  along  that  line, letÆs work  through  a  typical
situation. Assume you want to setup an æAnonymousÆ FTP  site.
This  needs a directory tree with all the goodies  the  users
might want to download, for which they need read access.  You
also  need  an  upload directory where users can  upload  new
goodies,  but you donÆt want others to be able to immediately
get  their greedy fingers on it, since you want to check  for
viruses first. So, this upload directory needs write  but  no
read  access. We decide to put everything on the big  network
drive,  æY:Æ, under the æANONFTPÆ directory. We  also  create
the  æUPLOADÆ directory here for uploads. In Serv-U we  would
create  the  user æAnonymousÆ with the following access  path
rules (and in this order):

     Y:\ANONFTP\UPLOAD     - write, inherit rights
     Y:\ANONFTP            - read, list, inherit rights

Reversing the rules will not work: If a user tries  to  write
to  the  upload directory, the security mechanism will  check
against   Y:\ANONFTP   and  conclude   that   UPLOAD   is   a
subdirectory, so the rule applies, and the rule  grants  only
read and list access. Please take note that write access does
not  allow  a user to get a directory listing of  the  UPLOAD
directory,  so  not  only wonÆt a user be  able  to  download
anything from there, the user cannot even see what files  are
uploaded.

If  the drive letter is left out of a path, it applies to all
drives. So, a fast way to get full access to all files on all
drives is:

      \                    - read, write, delete, list, make,
                             remove, and inherit rights

Now, the same mechanism that determines access to directories
also  applies  to  files. It is possible to grant  access  to
specific  files on a per-file basis. LetÆs take the  previous
example about the anonymous FTP server. We want to put a file
æSECRET.TXTÆ in the ANONFTP directory, but nobody is  allowed
to  read  it of course. So, our access paths list would  look
like this:

     Y:\ANONFTP\SECRET.TXT - no rights
     Y:\ANONFTP\UPLOAD     - write, inherit rights
     Y:\ANONFTP            - read, list, inherit rights

Again,  the  order of the paths is important!  The  directory
access   rights   do   not  have  any  meaning   for   files.
Alternatively,  if SECRET.TXT was a directory  instead  of  a
file,  the above settings would keep users completely out  of
this directory.

2.5 How to Setup Anonymous Access
---------------------------------

Since setting up anonymous access is such a common task  when
running a FTP server, I want to present a separate section on
this  subject. It is not much different from setting  up  any
other user, so this is going to be a æfollow the recipeÆ kind
of instruction, with the specifics for anonymous thrown in.

First,  a  tip:  If you are running Windows 95  it  might  be
worthwhile to create a new æDriveSpace 3Æ volume with all the
files you want to make available. This not only provides  you
with  a  lot  more  space  due to the compression  (which  at
regular  FTP speeds has no impact on performance),  but  also
effectively isolates the users from more sensitive areas like
your  C: drive. So, for the rest of this story I will  assume
you just created a DriveSpace volume named æF:Æ.

LetÆs say all the good stuff for our users is going to be  in
subdirectories of F:\ANONFTP, and we want to allow uploads of
new files to the F:\ANONFTP\UPLOAD area.

The  first task in setting up anonymous access is creating  a
user  with  this name. Thus, go ahead, pull up the  æSetup  -
UsersÆ  menu and its dialogbox. Fill in the æUsernameÆ  field
with æAnonymousÆ. The æGroup nameÆ and æPasswordÆ fields stay
blank, since they are ignored for anonymous anyway. Now,  the
æHome  directoryÆ  field needs to be set to F:\ANONFTP  since
that  is  the point we want the users to start when they  log
in.

When they log in we want to let them know the especially good
things and give them instructions on how to upload, and to do
that  we  need a login message file. Netscape will show  such
files  in  a  very  nice  way, at the top  of  the  directory
listing.  So, letÆs create a file named LOGANON.TXT with  the
following contents:

     Welcome %name from %IP!
     For  the  latest in natureÆs feline beauty see directory
     IMAGES
     You can hear them in the directory MEOW
     Please  keep uploads smaller than 100 Kb and place  them
     in UPLOADS

Since  I  can imagine that not everyone envisions  cats  when
hearing  about æpretty picturesÆ please feel free  to  change
the  text  according to your wishes! The words starting  with
æ%Æ  are directives to Serv-U which will be replaced by  real
text  when the user logs in. æ%nameÆ becomes the userÆs name,
and  æ%IPÆ  either the IP number or the IP name of  the  user
(whichever  is available). There are many more æ%Æ directives
and you can find more information about these in the æHow  to
use sign-on and/or sign-off messagesÆ section.

Now  letÆs  place the file LOGANON.TXT in F:\ and thus  enter
F:\LOGANON.TXT in the æMessage fileÆ field.

WeÆre  almost there, but the users still need access to those
directories.  So click the æAddÆ button and  enter  the  path
F:\ANONFTP.  When this is done the access rights are  already
set,  since the default of æreadÆ, ælistÆ, and æinheritÆ  are
exactly  what  we  want. Now for the upload directory:  Click
æAddÆ  again and fill in F:\ANONFTP\UPLOAD. Serv-U will place
this above the previously entered access rule, which is good.
However,  the access rights are not exactly what we want,  so
uncheck æreadÆ, check æwriteÆ and uncheck ælistÆ. You  should
now  have the following two access rules in the list (In this
order!):

     F:\ANONFTP\UPLOAD     - write, inherit rights
     F:\ANONFTP            - read, list, inherit rights

This  is  all  we have to do in the æSetup UsersÆ  dialogbox.
Just  check  if  æEnable accountÆ is checked,  which  is  the
default. To store it press æStoreÆ.

There  are a few more things that are important for anonymous
access.  They  can all be found in the æSetup -  FTP  ServerÆ
menu  choice. The first field of interest to us is  æMax  no.
anonymousÆ, this determines how many anonymous users  can  be
logged in at the same time. If you leave this blank then Serv-
U will allow any number. Use your own judgment what you think
your  machine can handle. Next is æTime-out anonymousÆ.  This
determines how long Serv-U will wait when anonymous users are
not  doing  anything before kicking them off the server.  The
default  of  15 minutes is a good value, still allowing  slow
transfers  and  bad  connections to work  while  keeping  the
server reasonably clean of all those Netscape users that stay
logged in after their transfer is long done. Setting the time-
out  to  0 or leaving it blank means that Serv-U wonÆt  check
how long a user has been idle.

This brings us to the æRelative paths anonymousÆ checkbox. By
default this is checked and it causes anonymous users to  see
all  directories  and  path  names  relative  to  their  home
directory.  So, if your anonymous users have æF:\ANONFTPÆ  as
their  home directory, they will receive back æ/Æ  when  they
inquire with the PWD command. Similarly, every reference they
make to a file or a change of directory is taken relative  to
this path. The main reason it is in there is because most WWW
browsers  need æchange directoryÆ access to the  æ/Æ  (=root)
directory to make them work. This way they believe they  have
access  to  the root and are happy, while on a PC  you  donÆt
always want to give users access to your real root directory.
The  disadvantage of having this mechanism is that  anonymous
users  are restricted to their home directory and below,  nor
do  they have access to other drives. Sometimes you want them
to  be able to have access outside their home directory  tree
and  unchecking this option will allow that. Anonymous  users
will then be treated like any other user as far as path names
are  concerned  and they will be able to change  to  parallel
paths  and  other drives if their access rights permit  this.
The  price  you pay is that unless you provide some  form  of
access to the root of their home directory, i.e. æF:\Æ in our
example, WWW browsers wonÆt be able to log in.

The last item we need to concern ourselves with for anonymous
users is the æCheck anon. passwordsÆ option. By default  this
is  unchecked,  which  means that anonymous  users  can  type
anything  as  a  æpasswordÆ to get into the server.  If  this
option is checked, then Serv-U makes sure that the æpasswordÆ
entered by anonymous users is something that looks like an E-
mail address. Netiquette prescribes that anonymous users send
their E-mail address as a password, alas this good custom  is
disappearing  fast and the latest version of Netscape  (v2.0)
does not even have the ability to do this anymore. So, unless
you  want  to severely restrict access and teach people  good
manners it is probably best to leave this unchecked.

Just  so  you  know: As is customary for FTP servers,  Serv-U
also  looks for a æ-æ (hyphen) as the first character of  the
anonymous  æpasswordÆ. If present, all  login  and  directory
change messages are suppressed.

Well,  you made it through and now know just about everything
there  is to know about setting up anonymous access  to  your
server. You can enhance things further with sign-on and sign-
off  messages, directory change messages and links, which are
covered in the following sections.

2.6 How to Use Groups
---------------------

To ease the burden of maintaining a large site somewhat, Serv-
U  uses  the  concept of ægroupsÆ. This allows you  to  group
together  users  with similar settings. All the  similarities
are  stored  in  the  group  information,  leaving  only  the
differences per user for you to set up.

To  edit groups select the æSetup - GroupsÆ menu choice.  The
dialogbox you see should look familiar by now: ItÆs the  same
one  as  for the user setup. So, if you know how  to  set  up
users, you also know how to set up groups! The only item that
is not applicable for groups is the æUsernameÆ field, so this
is  grayed  out,  instead you use the æGroup nameÆ  field  to
specify the name of the group you are editing.

To  show  the power of groups a quick example: LetÆs say  you
are  the Pentagon system administrator and want to create FTP
access for everybody in case they are on field trips. So, you
hook  up  this old PC to the net, install Serv-U and register
it  (Hypothetical situation). Then you proceed  to  create  a
group æStarWarsÆ. Now you go on to set the password for  this
group to æRonaldRÆ, and their home directory (all their files
are shared anyway) to æy:\super\secret\starwarsÆ. You fill in
some  access path rules as well, and youÆre all set: The only
thing  left  is  entering the user names, you donÆt  have  to
provide any other information per user. A 10 minute job.

Now  thereÆs this occasional guest user, æBillyCÆ. You  donÆt
want  him to get into certain directories, so you make him  a
member  of the group but specify those secret directories  in
his access path rules with æno accessÆ, and youÆre all done.

As  you  already  saw  from  the previous  example  the  user
settings have precedence over the group settings. This allows
you  to  selectively  override certain  parts  of  the  group
settings,  making groups a very flexible mechanism  for  user
maintenance.  To  summarize: Serv-U first checks  the  userÆs
settings, then looks if the user is part of a group and if so
uses  this groupÆs settings, and finally, if nothing is found
yet  the settings of a user with name æALLÆ are used if  they
exist.  The  only  user that cannot be used together  with  a
group  is  æAnonymousÆ. For security reasons  only  the  user
settings themselves are used here.

Well, by now you know most of what there is to know to run  a
smooth Serv-U FTP server. The next sections are mostly  about
goodies  that make life easier or more colorful. Next  youÆll
learn how to find out what users are doing on your server and
if they are nasty, how you can boot them off.

2.7 How to See Who is Logged In
-------------------------------

Even  though Big Brother might not be watching you,  you  can
certainly  watch your users! Select the æFile  -  User  InfoÆ
menu  choice  and  up pops the user information  window.  The
upper  part shows a list of all users currently connected  to
your  server. By clicking with the mouse on one of the  users
you  can  get extra information about that user in the  lower
part of the window.

There  are  a  few  things  to keep in  mind  concerning  the
displayed  statistics: The IP name is found by  initiating  a
reverse DNS lookup of the IP number. It can take time  before
an answer comes back from the DNS server, and there are quite
a  few IP numbers that do not have an IP name. So, it is  not
at all unusual for a user not to have an IP name.
Then,  the  transfer speed displayed should not be taken  too
absolute.  Since the socket stack buffers any  send  activity
(Serv-U can write lots of bytes to the stack in a very  short
time, after which the stack sends it off at its leisure)  the
indicated speed can be much higher than it actually is. Also,
if  there are local transfers going on with a very high speed
then Serv-U and the socket stack can get into a tight loop of
sending or receiving, and the user information might not  get
updated  for  some time. This is normal ("Not a  bug,  but  a
feature!").

This  brings us to the æShow CommandsÆ button. Pressing  this
will  pop up another window which will show you all  the  FTP
commands  the  user  sends and the replies  from  Serv-U.  It
tracks  the commands of the in æUser InfoÆ selected user  and
by clicking on another user you can switch.

The  last  button of interest in this window has the  prosaic
name  æKill  UserÆ. This is the place where, if so  inclined,
you can alleviate all your frustration after a bad day at the
job.  For  that reason the entire next section is devoted  to
it.

2.8 How to Kick a User Off the Server
-------------------------------------

If  someone is doing things you donÆt like, or you just  want
to be mean, Serv-U offers you the option of kicking that user
off your server and keeping him or her off.

This is done by selecting the æFile - User InfoÆ menu choice.
In the window that pops up as a result you select the user-to-
be-killed,  and proceed by pressing the æKill  UserÆ  button.
This  will  pop  up a little dialogbox asking you  if  youÆre
really sure about this, and offering several options to  keep
the user in question off on a more permanent basis.

You  will see two checkboxes. The first is æRefuse IP  access
in  futureÆ. If you check this and then press æOKÆ the userÆs
IP  address will be added to the list of IP numbers that  are
refused  access. This will prevent that user from logging  in
again,  or at least it not from the same IP number.  We  will
talk  about  access and IP numbers in greater detail  in  the
QHow to limit access by IP number sectionÆ.

The  second  checkbox is æDisable accountÆ and checking  this
does exactly that: The æEnableÆ checkbox in the æSetup UsersÆ
dialogbox will be unchecked. Nobody will be able to use  that
login name until the account has been enabled again.

2.9 How to Setup Logging
------------------------

When  you  select the æSetup - LoggingÆ menu choice you  will
see a dialogbox that lets you specify what events you want to
log  and  where to log them to: either to screen only  or  to
both the screen and a logfile.

The first two items deal with logging to a logfile. The first
one,  æEnable logging to fileÆ switches writing to a  logfile
on  or  off. The second item, æLogfileÆ is meant for entering
the  path  and  file  name into which all  the  messages  are
written.  Of  course, logging will only  work  when  a  valid
logfile  name  is  entered, it has to be  a  full  path  name
including a drive letter.

Serv-U  gives you a wide choice in what should be  logged  or
not. In all there are seven different categories that can  be
individually  enabled  or  disabled.  The  items   are   self
descriptive  except maybe for three: æLog FTP commandsÆ  logs
every  command as it is received by the server and  æLog  FTP
repliesÆ logs the command replies that are sent back  by  the
server  to the client. These two options are mainly  intended
for  diagnostic purposes and are switched off by default. The
last  option is æLog IP namesÆ and when checked, Serv-U  will
try  to  find  the IP name of a user by doing a  reverse  DNS
lookup  on  the IP number. Keep in mind that DNS lookups  can
take  just  about any amount of time, cost a fair  amount  of
overhead,  and  not all IP numbers have a IP name  associated
with  it. When this option is checked the IP name of  a  user
will be logged as soon as it becomes available.

Messages  are always logged to the Serv-U window,  regardless
of  the logfile settings. There is no difference between  the
messages on screen and the ones in the logfile, although some
things  are  only shown on screen. The latter are server  and
program  related matters, like version number,  server  going
on/off-line etc.

Log  messages  always have the same layout.  The  reason  for
using such a strict format is to make it easier to search for
specific  messages  or certain types of messages.  This  also
makes  it  possible  to  do automatic accounting  by  machine
reading  the logfile if you need it. The logfile can be  read
or  copied at any moment, even when Serv-U is running (It  is
also  possible to get the file via FTP using Serv-U itself!).
The format is as shown below, in stylized form:

     [n] DATE TIME - (xxxx) MESSAGE

The first number, ænÆ, indicates the type of message that  is
being logged. Currently there are six different categories:

     1    - system messages (problems etc.)
     2    - FTP commands (from client to server)
     3    - GET file transfers
     4    - PUT file transfers
     5    - security related events (users logging in etc.)
     6    - FTP replies (from server to client)

The  second  number, æxxxxÆ, is a unique  ID  assigned  to  a
client  the  moment  the  connection  is  made.  All  further
messages  concerning that client will use  the  same  number.
Again,  this  was  done  to  make it  easy  to  do  automated
accounting,  or,  to  find  back events  using  the  æsearchÆ
facilities of every editor.

You  can  rename, move or delete a logfile at any time  while
the  server is running, there is no need to stop the  server.
You  can even copy a logfile to a remote system using  Serv-U
itself!  If you want to temporarily stop logging to file  and
see  it  on screen only, you can uncheck the æFile - LoggingÆ
option  in  the  main menu. Needless to say this  has  to  be
checked to enable logging to file.

One more note: If you log GETs and PUTs then Serv-U will also
tell you the average transfer speed. For GETs the value Serv-
U  shows can be a bit optimistic, especially for small files,
as  a result of the socket stack buffering the bytes that are
sent over the network. Serv-U can very quickly transfer 10-20
Kbytes into the socket stack, which then proceeds to send  it
over  the network at its own leisure. However, Serv-U has  no
way  of finding out when the actual transfer is complete, and
assumes  that when it has sent the block to the socket  stack
it is done.

Enough boring talk, letÆs get back to the fun part! Next will
be  explained how you can pour your heart out to  your  users
through all kinds of messages.

2.10 How to Use Sign-on and/or Sign-off Messages
------------------------------------------------

Your  FTP-server can display a welcome message every  time  a
user connects to it. This can be very useful to provide users
with  information about your FTP server, like where  to  find
games, or æSerious SoftwareÆ. Likewise, you might want to say
good-bye to them when they leave, or remind them to send that
check  . . . The way to do this is by entering a text in  the
QSign-on/Sign-offÆ dialogbox which pops up  when  you  choose
the æSetup - Signon/offÆ menu choice.

There  are several special words that you can enter  in  your
sign-on and sign-off text which get expanded while being sent
to a client. They all begin with æ%Æ. Here is the list:

     %time         - displays the current time on your PC
     %date         - displays the current date on your PC
     %unow         - displays the current number  of  Serv-U
                     users connected
     %uall         - displays the number of users since  the
                     server was started
     %u24h         - displays the number of users in the  last
                     24 hours
     %maxusers     - displays the maximum no. of users, as set
                     in æSetup - ServerÆ
     %maxanonymous - the maximum no. of anonymous users, as
                     set in æSetup - ServerÆ
     %name         - displays the userÆs login name
     %ip           - displays the userÆs IP number or name  if
                     available
     %dir          - displays the userÆs current directory
     %disk         - displays the userÆs current disk drive
     %dfree        - displays the amount of free disk space on
                     the userÆs current disk
     %fup          - displays the number of files uploaded  by
                     the current user
     %fdown        - displays the number of files downloaded
     %ftot         - displays  the  total  number  of  files
                     transferred
     %bup          - displays the number of bytes uploaded  by
                     the user
     %bdown        - displays the number of bytes downloaded by
                     the user
     %btot         - displays  the  total  number  of  bytes
                     transferred
     %tconm        - displays the total connect time in minutes
     %tcons        - displays the connect time in seconds - to
                     be used with æ%tconmÆ

Not  all  of these directives make sense for both the  signon
and signoff text: There is little point in putting æ%diskÆ in
the  signon  message, since the user is not  yet  logged  in.
Likewise  for  some  other directives.  However,  these  same
directives can also be used in directory change messages  and
login  messages, which are covered in the following sections.
There they can be very useful.

You could make the following signon text:

      Welcome, it is %time on %date, and you are user number %unow
      Over the last 24 hours, %u24h people have visited this site

IÆm  sure  youÆll figure out by yourself what this will  look
like to the user . . .
Please  keep  in  mind that the average client  has  only  80
characters per line, and the first four are taken up  by  the
reply code. So keep your lines short if you want the users to
actually see your prose.

2.11 How to Setup User Specific Login Messages
----------------------------------------------

After  astonishing the user with your signon message you  can
go  for  the  kill  by also providing a user  specific  login
message.  These messages should be put in one  or  more  text
files  and  the file name can be filled out in the  users  or
groups setup dialogbox, in the æMessage fileÆ field.

The  file name you enter in the æMessage fileÆ field can have
several forms: You can use an absolute path with a drive, for
example  C:\FTP\LOGMES.TXT. This will of course  make  Serv-U
use  this  file. You can also specify only the name,  and  no
path, for example LOGMES.TXT. This will cause Serv-U to  look
in the userÆs home directory for this file and if it is there
it will be displayed to the user. Finally, you can specify  a
path  but no drive letter, for example \FTP\LOGMES.TXT.  This
means  that  Serv-U  will add the drive of  the  userÆs  home
directory  to  make  a  full path. The  latter  two  ways  of
specifying the file can be very useful for groups, i.e.  with
just  a single file name set up you can provide all the users
that are part of that group with a separate login message.

Of  course,  you can use all the æ%Æ directives mentioned  in
the previous section in login messages. Try for example:

     Hello %name from %IP!

With a little luck Serv-U will have found the IP name of  the
user  by the time he or she logs in. So you can impress  them
by   showing  you  know  where  they  are  (Big  Brother   IS
Watching!).  By the way, Netscape displays the login  message
in  a  nice looking way at the top of the screen (The sign-on
message does not get displayed by Netscape).

2.12 How to Use Directory Change Messages
-----------------------------------------

It  can be very useful to tell a user some specifics when  he
enters  a  directory. For this purpose Serv-U  has  directory
change  messages. There can be a different message  for  each
directory.

As with the login messages, the directory change message text
should be stored in a file. In the æSetup - FTP ServerÆ  menu
choice you can specify which file name Serv-U should look for
when  the  user changes directory. You can specify  the  file
name  in two different ways: First is an absolute file  name,
for  example  C:\FTP\CDMES.TXT. As  youÆd  expect  this  will
display  that  file  for each directory change.  Then  it  is
possible  to  use  a  file name only without  the  path,  for
example CDMES.TXT. This will make Serv-U look for and display
the file with that name, in the directory into which the user
is changing. The latter one is the usual way to use directory
change  message files, since this enables you  to  specify  a
different message for each directory.

Like sign-on and sign-off messages you can use any of the æ%Æ
directives in directory change messages. Take a look  at  the
previous sections for a list of all directives.

Netscape will display those directory change messages at  the
top  of the page. One more trick: Anonymous users cannot  see
æhiddenÆ  files. Hidden files are files with the  DOS/Windows
æhiddenÆ  attribute set, something you can do using  the  DOS
program æAttribÆ or by changing the æpropertiesÆ of a file in
Win95  (using the right mouse button). So, if you  make  your
directory change message files hidden they wonÆt show  up  in
the directory listings while anonymous users still get to see
the messages.

2.13 How to Use Links α la UNIX
-------------------------------

Now  for  the  piΦce de resistance (pardon my French),  which
sets Serv-U miles apart from any other FTP server that I know
of for MS-Windows: Links!

If  you know UNIX then you know what I am talking about  when
links  are  mentioned. If not, then try the following:  Links
are  names  of  files and/or directories that appear  in  the
directory listing but they are not in the directory that  the
user  is  listing. Rather, they point to the actual directory
or  file and can be used by the user as if they were the real
thing  itself. A little like the Windows 95 æshortcutsÆ,  but
more  real: When you delete a link through Serv-U the  actual
file  or  directory is gone! The great value of links  is  in
showing  users that you have all kinds goodies  available  on
other  disk drives. The user can then simply æcdÆ to  a  link
and   thus  change  to  a  completely  different  drive   and
directory.

The  way  Serv-U works with links is by reading them  from  a
text  file.  You can have different files and thus  different
links  for  each  directory, much in  the  same  way  as  the
directory  change messages work in the previous section.  The
file  name  is  entered via the æSetup  -  FTP  ServerÆ  menu
selection  (Guess where!). As with message  files  there  are
several  ways  to specify which file Serv-U  should  use  for
links:  You  can  enter a file name by  itself,  for  example
LINKS.TXT.  This makes the server look in the userÆs  current
directory for a file with this name and if found it is merged
into  the  directory  listing. This is  the  way  to  set  up
different link files for each directory. The second method is
by specifying a full path name, for example C:\FTP\LINKS.TXT.
As  youÆd  expect the result will be that the same links  are
shown in each directory. Finally, you can leave out the drive
letter,  for example \FTP\LINKS.TXT, which means Serv-U  adds
the  current drive to the name and then looks for  the  file.
Useful  for setting up links that change per drive,  but  not
per directory. If you make the link fileÆs attribute æhiddenÆ
then  anonymous  users wonÆt see the file  itself  appear  in
their  directory listings while they still  get  to  see  the
links.

Now, what should a link file look like? Each line of the file
describes a different link. First comes the link name,  which
is  what  the user is going to see in the directory  listing,
then a æ|Æ which acts as a separator, and finally the file or
path  that the link should point to. Here is an example  link
file that should make all this a little clearer:

     D-Drive         | d:\
     CD-ROM          | f:\
     Home            | ~
     Fun Stuff       | g:\public\games
     One up          | ..
     Pointless       | \junk\..\more\..
     Poem            | c:\culture\poem.txt

As  far  as the user is concerned links behave like the  real
thing: They can be used for æcd æ if itÆs a directory,  ægetÆ
for  a  file  etc. Only difference is that  if  a  link  gets
deleted  the file or directory it points to will get  deleted
but  the  link  will  continue to show up  in  the  directory
listing. Needless to say that it is your responsibility  that
the links in a link file point to something that makes sense.

So  much  for the fun part, back to more serious matter  with
more  about how to select whom you want to let on your server
and whom to bounce. . .

2.14 How to Limit Access by IP Number
-------------------------------------

This  æSetup - IP AccessÆ menu choice will pop up a dialogbox
which  provides  the  means to restrict access  to  your  FTP
server to certain IP-numbers. If  for example, you work at  a
university and only want your faculty members to be  able  to
access the server, then this is a great way to do it. In  the
upper left corner of the dialogbox you can choose which  type
of  rules  you want to specify: æDenyÆ or æAllowÆ rules.  The
deny  rules  decide who should be kept out, the  allow  rules
indicate  who should be welcomed. THE ORDER OF THE  RULES  IS
IMPORTANT! When a client contacts the server, the deny  rules
are  looked  at  FROM TOP TO BOTTOM. If no matching  rule  is
found,  the  allow  rules are evaluated, again  from  top  to
bottom.  The  first matching rule applies, and evaluation  is
stopped. If there are no IP-access rules everybody can  enter
the  FTP  server.  As soon as there is one rule,  only  those
clients that pass the rule check are allowed to enter.

You  can  type in a new rule in the æRuleÆ edit and then  use
the  æAddÆ  button to add the rule to the list. The  æRemoveÆ
button will remove the currently selected rule from the list.
To  change the order of the rules you have to select  one  by
clicking  the mouse on it, and then use the æUpÆ  and  æDownÆ
buttons to move it around.

Rules  are  nothing more than IP-numbers  or  ranges  of  IP-
numbers. There are two special characters: the star  æ*Æ  and
the  hyphen æ-Æ. A star functions as a wildcard for  checking
the number. Any number will match that section of the rule if
it  is  a  star.  The  hyphen is used to denote  a  range  of
numbers. Simply separate the starting and ending values by  a
hyphen. For example, say all IP-numbers in your company  look
like 134.56.34.xxx with æxxxÆ being any number. Now, you want
to  restrict  access to your FTP server to other  members  of
your  company only. The way to do it is to create an  æAllowÆ
rule that looks like this:

     134.56.34.*

ThatÆs  simple,  isnÆt it!? Likewise, if you  know  that  the
competition  has IP-numbers in the range 168.76.xxx.xxx,  you
can keep them out of your server with the æDenyÆ rule:

     168.76.*.*

Now,  you  need  to  share some of  your  files  with  a  few
colleagues,  and management in your company is too  cheap  to
install a local network. You find out that their PCÆs have IP-
numbers  134.56.34.128, 134.56.34.129 and 134.56.34.130.  You
could  of course make three æAllowÆ rules, each with  one  of
these  numbers. A faster way to do this is to make  a  single
rule like this:

     134.56.34.128-130

The  special characters æ*Æ and æ-Æ donÆt need to be  at  the
end  of the IP-numbers, any place will do. The rule 221.*.76-
154.89 is perfectly OK. I wouldnÆt know when youÆd need this,
but,  hey, the world is a strange place! Remember,  order  is
important  and  deny  rules are always evaluated  before  the
allow rules. Experiment a bit, and youÆll get the hang of it.

Since  people  keep  asking me this: A few  words  about  the
security  of  IP-access rules. The check on IP number  stands
pretty  much at the top of the Serv-U security mechanism  and
all  connections  have  to pass through  this  rather  narrow
bottle  neck. The code that does the checking is quite simple
(In  contrast to the code that does the access rule  checking
for paths), so it is unlikely that there are any loopholes or
bugs  left in there. So, in my humble and honest opinion this
is  one  feature that makes for a very secure FTP  server  if
that is what you need!

2.15 How to Print via FTP
-------------------------

Serv-U  also  allows  access to all PC  ports:  PRN:,  LPT1:,
LPT2:,  LPT3:, LPT4:, AUX:, COM1:, COM2:, COM3:,  and  COM4:.
This  can  be  a  convenient way of setting  up  a  ænetworkÆ
printer by transferring files directly to PRN: or LPT1: using
FTP. These ports are treated like any regular path name, so a
user needs access rights to use them. Thus, to make a printer
on  PRN:  accessible and a modem on COM2: the user needs  the
following   access   rights  in  the   æSetup   Users/GroupsÆ
dialogbox:

     PRN:                  - write and delete rights
     COM2:                 - read, write and delete rights

There seems to be much confusion on how to actually use  this
feature,  therefore a short explanation. These  ports  behave
very  much like files that always exist and can be  found  in
every  directory  although they donÆt show  up  in  directory
listings. So, no æcdÆ commands are needed, just transfer your
file-to-print  to the port with the printer.  For  a  command
line  FTP client this would look like æput FILE.TXT PRN:Æ  to
print  file FILE.TXT on a printer attached to port PRN:.  For
point-and-click type FTP clients you have to specify that  it
should  ask  you  for the destination file name.  Then,  when
prompted  for the destination file name you enter  æPRN:Æ  or
another  port  of your choice. For example, for  the  popular
client  WS_FTP you have to check the æPrompt for destinations
file  namesÆ  option in the æSession OptionsÆ section.  After
doing  that  you can simply upload the file-to-print  and  it
will  ask you for the destination, for which you fill in  the
printer port name.

The  above procedure should work well to print ASCII text and
text-based   protocols  like  PostScript  (If  your   printer
supports  it).  However, with binary files your  mileage  may
vary:  It seems that the port closes when a ^D is encountered
in the stream that is being printed.

2.16 How to Execute Programs via FTP with Serv-U
------------------------------------------------

Serv-U  allows you to start DOS or Windows programs  remotely
using a FTP client. Keep in mind though that Serv-U is not  a
Telnet  server,  and any program output or  windows  will  be
displayed  at  the PC where Serv-U is running.  However,  for
many  applications the ability to start a program is  enough,
or  you might be able to redirect input and output, i.e. like
æMYPROG.EXE < INPUT.TXT > OUTPUT.TXTÆ.

The  first  requirement to using remote program execution  is
that  the  user needs sufficient access rights to  start  the
desired programs. This is controlled by the æexecuteÆ  access
right  in the æSetup Users/GroupsÆ dialogbox. You can  either
give a user execute access to the directory where the program
can  be found, or you can specify the exact program name. For
example,  if  we  want  to  be able  to  execute  COMMAND.COM
remotely,  and  this  program can  be  found  in  the  C:\DOS
directory, then the following access rule would do the trick:

     C:\DOS\COMMAND.COM    - execute access

Now, to actually start a program remotely you need to use the
FTP  command  æSITE  EXECÆ from the FTP client.  Usually  you
cannot  do that directly, since the client doesnÆt understand
this command, and you need to tell the client to send it as a
literal string to the server. for example the UNIX FTP client
(and  others like it, as the one that comes with  Windows  95
and  NT)  uses the æQUOTEÆ command for this purpose.  So  the
full  command line to let COMMAND.COM copy a file from  A.TXT
to B.TXT would become:

     QUOTE SITE EXEC C:/DOS/COMMAND.COM COPY /B A.TXT B.TXT

You  might notice the use of æ/Æ instead of æ\Æ in the  path.
This  is  because most command line FTP clients do  not  take
kindly to backslashes. For Serv-U it doesnÆt  matter and  you
can  use  æ/Æ  and æ\Æ alike. You can also  see  that  it  is
possible  to  specify  arguments to a program  as  you  would
usually do, Serv-U passes them on to the program. The example
above will likely only work for command line FTP clients that
are  based  on  the  UNIX  client. For  point-and-click  type
clients, like WS_FTP you are on your own. They may or may not
have  the ability to send literal commands to the server  but
the way to get that done will vary from client to client.

Starting programs remotely may not be as straight forward  as
it  seems,  and  can  have varies side  effects.  Also,  some
programs  need  to  be  started via the command  interpreter,
COMMAND.COM,  others not. In short: Some  experimentation  is
recommended!

One  more  important thing about æexecuteÆ  access:  Although
Serv-U checks the programÆs path for access, the program  you
start  this way is free to access and delete any file in  any
directory  on  your  computer! Also, if  you  give  æexecuteÆ
access to a directory then any program in the DOS path can be
started! In short: Be very careful with æexecuteÆ access,  as
this is a very big potential security hole!

2.17 How to Use Serv-U with æSLIP/PPP EmulatorsÆ
------------------------------------------------

More  and  more  Internet  Access Providers  these  days  are
offering Internet connections that are not ærealÆ. Instead of
having  their own IP address these connections run on top  of
the  IP  address of a UNIX host system. The general name  for
this  category of connections is æSLIP/PPP emulatorsÆ  and  a
few of the popular programs that will do that are æTIAÆ (=The
Internet  Adapter),  æTWinsockÆ, and æPipelineÆ.  The  reason
ISPÆs use them is because they offer a cheap way to get  many
people  connected  to  the net. They usually  work  fine  for
programs  like Netscape, mail, and FTP clients. However,  for
servers they come with a number of build-in disadvantages.

Because  of  the way they have to do their work they  have  a
number  of  peculiarities. Since the PC has to share  the  IP
number with the host system you will generally not be able to
use  the default port 21 for Serv-U. Instead, you either have
to  use  a high port number (generally above 8000) or set  up
'port  redirection'. Ask your Internet provider  for  details
about  the  latter. A related problem is that the  IP  number
displayed by Serv-U is, in this case, not the IP number  that
clients  should use to contact your server. It  is  merely  a
dummy  to  keep  the socket stack of the PC  happy.  For  the
outside  world the IP number of your server is  the  same  as
that  of the emulator host system, i.e. that of your Internet
provider. Another special effect is that clients will not  be
able  to  use 'passive' mode for data transfers.  This  means
that  regular FTP clients will work OK, but WWW browsers like
Netscape and Mosaic will not work when Serv-U runs via a SLIP
emulator.  For  the same reason it won't be possible  to  use
clients that are also connected via a SLIP emulator either.

Just  in  case you are interested IÆll give you the technical
details  behind all this. Since Serv-U has to  share  the  IP
number  with the Internet connection host system  (Usually  a
UNIX system), the usual FTP port (number 21) will most likely
be  already in use by the host system. Because at a single IP
address there is only a single port 21 this means either Serv-
U  or  the host has to move to another port. The second  side
effect has to do with the socket stack: They usually need  to
know  their  own IP address to do the work, and to  keep  the
stack  happy  it is installed with a non-existent  IP  number
like  192.0.2.1  (Seems  to  be a popular  choice).  The  FTP
protocol  does  not use the server side IP number  much,  the
only  exception is the FTP æPASVÆ command, which is used  for
passive mode data transfers (Which all WWW browsers use).  In
essence, what the PASV command does is ask the server for  an
IP  address and port number where it will listen for the data
connection.  Since  the FTP server does  not  know  that  its
address  is bogus, it will trustfully report this  back.  The
client will then try to connect to this dummy address,  which
of course will never work.

2.18 How to use Netscape to access Serv-U
-----------------------------------------

You  might  not  be aware of it, but Netscape and  other  WWW
browsers  can  do  a whole lot more than just  anonymous  FTP
access. The general syntax for FTP is the following:

     FTP://<user>:<password>@<IP address>/<path/file>

Very  little of this is needed and in its simplest  form  you
only  use  the  <IP  address>  which  results  in  the  usual
anonymous  access. If you add a <user> section  (leaving  out
the password) then Netscape will prompt you for a password if
needed.  Of  course,  you can also specify  the  password  by
yourself by adding the <password> section. So far we did  not
use  the <path/file> section and this means the user will end
up  in his or her home directory. If you want to go somewhere
else  you  can tell Netscape to do this with the  <path/file>
section.

In the <path/file> section you should use æ/Æ instead of æ\Æ,
and  you can add a drive letter as part of the path.  So,  to
finish up with an example that uses all of the above:

     FTP://john:[e-mail]/f:/john

This would log John into the Cat Soft server.

By the way, did you know that the newest version of Netscape,
v2.0, can also upload files to a FTP server? To do so, simply
drag  the  file-to-upload  from æExplorerÆ  (the  Win95  file
manager),  or from the æFile ManagerÆ (in NT or Windows  3.1)
to the Netscape window and drop it there. Experiment & Enjoy!

2.19  How to Let the Whole World into Your Server (and Delete
All Your Files)
-------------------------------------------------------------

Even  for  those with a PC-oriented exhibitionist inclination
Serv-U  has  something to offer. You can let the whole  world
into your server and have them delete all your files. To  top
it off, if set up correctly they will reformat your hard disk
along the way too!

The  easiest  way to all that fun is to uncheck  the  æEnable
securityÆ  checkbox  in  the æSetup ServerÆ  dialogbox.  This
utterly  and completely disables all security in  the  server
and  thus offers the most comfort to your FTP users. Not only
can they freely copy and delete each and every file, they can
also  use  the  unique Serv-U feature that  lets  them  start
programs  remotely.  Of course, the fun  is  over  once  they
remotely  start FORMAT.COM, but what the heck,  it  was  nice
while it lasted!

Now,  for  those  that are a little æsarcasm inhibitedÆ  IÆll
spell it out: NEVER, NEVER, NEVER LEAVE THE æENABLE SECURITYÆ
OPTION  SWITCHED  OFF  IF YOUR SERVER  IS  CONNECTED  TO  THE
INTERNET!!!  This might all seem a bit overkill, but  believe
it or not, I quite regularly get E-mail from people that tell
me  they are running Serv-U exactly like that on the Net. Now
donÆt tell me I didnÆt warn you. . .

2.20 How to use multi-homed IP support
--------------------------------------

If  your  operating system supports it, and you have multiple
IP  addresses installed at your computer (Typically  this  is
done  in  NT),  you  can let Serv-U respond  differently  for
different IP addresses that the users connects to. To make it
a  little  clearer  a  small example: Say  you  have  two  IP
addresses   assigned   to   your   PC,   152.3.110.167    and
152.3.110.168,  which  correspond  to  IP  names   "ftp1.cat-
soft.com" and "ftp2.cat-soft.com" respectively. Now you  want
anonymous  users logging into the "ftp1" IP address  to  have
access  to different files and directories from those logging
into "ftp2". This is called multi-homed IP, and supported  by
Serv-U.

The  first  step  to  using this is  in  the  æSetup  ServerÆ
dialogbox. Press the button labeled æIP HomesÆ in there. Then
use  the  screen that pops up to enter all the IP numbers  of
your  PC.  When this is done you can go to the æSetup  UsersÆ
dialogbox, which will now show a new selection list with  all
your IP numbers. Just set up the users as you did before, and
select  the  appropriate IP number that should be  associated
with  that  user name.  This will allow you, for example,  to
make  several  users  named æanonymousÆ, each  responding  to
different  IP addresses. ThatÆs all there is to using  multi-
homed IP, it could not be easier!


3. The Inner Workings
=====================

Before  I  go  on to describe the settings of the  SERV-U.INI
file  I  want to spend a few words describing how Serv-U  was
made and how it goes about its job.

3.1 Serv-U Internals
--------------------

The  program was written using Borland C++ version 4.52  (for
the 16-bit version) and version 5.0 (for the 32-bit version).
To  check  for  shaky pointers and catch all  those  resource
leaks  the  program Bounds Checker version 3.01 from  Nu-Mega
was  used.  I think no serious Windows programmer  should  be
without the latter, very highly recommended!
This  whole  project started about two years ago  after  much
disappointment with the existing FTP servers for WinSock.  In
its current version it consists of a bit over 18000 lines  of
C++  code, divided into 29 C++ classes. The whole program was
constructed from scratch, not using any existing  FTP  server
code, and is tailored to MS-Windows and WinSock.

Internally, everything is very much compartmentalized,  using
a  different class for different partial tasks.  There  is  a
WinSock  class library, providing hi-level access to  Windows
Sockets and hiding all the nasty parts of dealing with  them.
It uses 100% asynchronous WinSock functions (also called ænon-
blockingÆ  functions)  thus avoiding problems  with  multiple
active sockets for a single task and re-entry. There is a FTP-
manager  class,  taking care of listening  for  clients,  and
setting  up  instances of the FTP-command  interpreter  class
when  this happens. The latter does the actual interpretation
of  the  FTP  commands,  talking to the  security  class  for
clearance  and  the  WinSock class for  communications.  Then
there are some utility-like classes, like those dealing  with
setup  and  logging.  By having all these  compartments  that
handle  very well defined tasks, I hope to be able to  easily
extend  this  FTP  server  and  fix  those  (hopefully   few)
remaining bugs quickly!

The  32-bit version of Serv-U is not multi-threaded, a single
thread  is used for all clients. æMulti-threadingÆ is one  of
those  buzz  words  that are poorly understood  by  most  and
abused  by  many. æThreadsÆ are light-weight processes,  that
can  be used to run concurrent tasks without all the overhead
of  creating real processes. In the mainframe world this  has
traditionally been used for servers: Each client would  start
a separate process or thread. However, unless you are running
NT  on a multi-processor machine (and I wager that now we are
talking  about  much  less than 1% of all NT  installations),
multi-threading is not generally going to gain  you  anything
because thread maintenance and switching brings overhead with
it.  There are still good reasons for using multiple  threads
on  a  single  processor machine: For independent  background
tasks, like a printer spooler, it makes perfect sense.  Also,
if  a process needs to perform multiple concurrent tasks that
each  would  take a long time (and ælongÆ in  computer  terms
could  mean anything over a few tens of milliseconds),  using
multi-threading is a good practice. However, for servers  the
practice  of  starting a separate thread for each  client  is
usually to provide an easy way out of programming the  thing.
That way the programmer can use æblockingÆ sockets and simply
block  (i.e.  ædo nothingÆ) until something  happens  on  the
socket stack. Makes for much simpler programs and is used for
all  the UNIX servers, so anything ported from there will  be
coded in this fashion. The better way to do things in Windows
is  to  make  the program event-driven and let it respond  to
messages from the socket stack instead of blocking the  task.
This  means æasynchronousÆ sockets have to be used,  and  the
whole  program is much harder to make: Instead  of  a  single
easy  to  follow  flow the program now becomes  a  number  of
message  handler routines that can be called  in  any  order.
Serv-U  only  uses asynchronous sockets, and the response  to
each  socket stack message normally does not take much  time.
Thus,  a  single thread can handle this perfectly  well,  and
cutting  it  up  in multiple threads would only  slow  things
down.

3.2 The SERV-U.INI File
-----------------------

All the settings for the server, users, and groups are stored
in  a  single file in text format. This file is always  named
SERV-U.INI.  When the program is started it  looks  for  this
file  in  a  number of different places: First the  directory
with  SERV-U.EXE  is checked. If no .INI  file  is  found  an
environment  variable  SERV-U is checked.  If  this  variable
exists  it  should  be  set to the path where  SERV-U.INI  is
found.  Finally, if this variable does not exist,  the  whole
DOS  path is scanned, including the Windows directories.  The
first SERV-U.INI file found on the way is used. If after  all
the  above  no  .INI file has been found,  the  program  will
create  one in the directory of  the Serv-U program.  Use  of
the  SERV-U  environment variable and the DOS path  makes  it
easy  to  set things up for network users where  there  is  a
single copy of the program but all the users needs their  own
settings. Serv-U uses the Windows built-in functions to  read
and  write  from/to the .INI file. A consequence of  this  is
that  the total size of SERV-U.INI can never exceed 64 Kbytes
on  Windows 3.1, 3.11 and Win95, limiting the number of users
that  can be set up. On NT there seems to be no limit to  the
.INI file.

WeÆll  now  go  over all the items that can appear  in  SERV-
U.INI. I will show you an invented setup file:

     [GLOBAL]
     Security=TRUE
     PortNr=21
     MaxNrUsers=15
     MaxNrAnonymous=10
     Invisible=TRUE
     Logfile=c:\serv-u\logfile.txt
     Logging=YES
     TimeoutUser=600
     TimeoutAnonymous=15
     TryOut=Crippled
     LogGETs=ON
     LogPUTs=ON
     LogSystemMes=ON
     LogSecurityMes=ON
     LogFTPCommands=OFF
     LogFTPReplies=OFF
     LogIPNames=ON
     RegistrationKey=S%FgdfsdEvG,Rob Beckers,Cat Soft
     AnonRelPaths=YES
     Window=100,100,400,300
     UserInfoWin=409,300
     DirChangeMesFile=index.txt
     LinkFile=link.txt
     CheckAnonPass=OFF
     Version=2.0.3.11

     [SIGNONOFF]
     SignOn1="Welcome to Robby's FTP-Server!"
     SignOn2="It  is  %time on %date and  you  are  user  no.
     %unow"
     SignOff1="Thanks for logging in!"
     SignOff2="Hope to see you again soon . . ."

     [IP-ACCESS]
     Bounce1=132.68.175.201
     Bounce2=223.*.*.*
     Allow1=132.68.176.53
     Allow2=132.68.175.*
     Allow3=101.43.23.30-40

     [USER=Anonymous@2]
     HomeDir=d:\anonftp2
     Access1=d:\anonftp2\upload,WP
     Access2=d:\anonftp2,RLP
     LoginMesFile=logmes.txt

     [USER=Anonymous@1]
     HomeDir=d:\anonftp1
     Access1=d:\anonftp1\upload,WP
     Access2=d:\anonftp1,RLP
     LoginMesFile=logmes.txt

     [USER=Rob]
     Group=system
     Password=WdRx.Jlk0kemm%
     HomeDir=c:\
     Access1=\,RWMCDLPE
     Access2=lpt1:,WM
     Access3=prn:,WM
     Access4=aux:,WM
     Access5=lpt2:,WM
     Access6=lpt3:,WM
     Access7=lpt4:,WM
     Access8=com1:,RWM
     Access9=com2:,RWM
     Enable=YES

     [USER=ALL]
     HomeDir=y:\
     Access1=y:\,RL
     Enable=NO

     [GROUP=SYSTEM]
     Access1=c:\system,RWDCMLEP
     Access2=d:\,RWDCMLEP
     Access3=y:\novell,RWDLP

     [IP-HOMES]
     IP1=152.3.110.168
     IP2=152.3.110.169

     [EXTERNAL]
     ClientCheckDLL1=CHKNOVELL.DLL
     ClientCheckDLL2=CHKNT.DLL


All  but  four  of  these settings can  be  changed  and  set
interactively  through the æSetupÆ menus. The exceptions  are
the entries for æInvisibleÆ, æRegistrationKeyÆ, æWindowÆ, and
æUserInfoWinÆ,  and if you really desire a user  to  have  no
password,  that  userÆs  æPassword=æ  entry  has  to  be  set
manually  (i.e.  nothing after the æ=Æ sign to  indicate  æno
passwordÆ).

The following paragraphs will describe each section and entry
in more detail.

[GLOBAL]
All  the settings related to the Serv-U program itself,  i.e.
the  functioning of the FTP server and system functions,  are
found  in  the  æ[Global]Æ section. For the file  formats  of
directory change message files and  link files please see the
appropriate æHow to . . .Æ section.

If  security should not be enforced, the æSecurityÆ entry can
be set to FALSE or 0. Doing so will leave the FTP server wide
open to everybody!!! Default value for æSecurityÆ is TRUE.

The  æPortNrÆ  entry determines the IP port that  the  server
will listen on. Default value is 21.

To  limit  the  maximum  number  of  simultaneous  users  the
æMaxNrUsersÆ  entry should be set to the desired  number.  No
entry  or  a negative number results in no maximum, only  the
number of available sockets will limit the number of users in
that  case. Similarly, the æMaxNrAnonymousÆ entry limits  the
maximum  number of æAnonymousÆ users. The value put  here  is
only   meaningful  if  it  is  smaller  than  that   of   the
æMaxNrUsersÆ entry.

For  system  managers  that donÆt want their  users  to  mess
around with the server settings, it is possible to make Serv-
U  invisible by setting the æInvisibleÆ entry to TRUE, or YES
and  put the Serv-U program in the æstartupÆ group. When this
is done the server will not show up in the task manager list.
One  consequence is that there is no way to stop the  program
short of exiting Windows. Default is NO for this entry.

The æLogFileÆ entry should specify a full path and name for a
logfile  if logging is desired. There is no default  logfile.
To actually switch logging on and off the æLoggingÆ entry can
be  set to ON or TRUE, or OFF or FALSE. Switching logging  ON
will  only  work  if  a  logfile  is  specified.  By  default
æLoggingÆ is set to ON.

The  entries æTimeOutUserÆ and æTimeOutAnonymousÆ  specify  a
time-out  in  minutes  for  respectively  regular  users  and
anonymous  users. If a FTP connection is left  idle  for  the
indicated amount of time it is automatically closed.  Filling
in  0  results in no time-out. Default values are 15  minutes
for anonymous and 10 hours for regular users.

The  next one deals with the way the program can be tried out
(when  there  is  no  registration  code).  æTryOutÆ  can  be
æCrippledÆ or æFullÆ. The first allows a user to do a maximum
of  5  GETs and 5 PUTs per session, switches the server  off-
line after 1 hour, and notifies clients that they are looking
at  an  unregistered try-out version. However,  it  does  not
contact my permission server. The æFullÆ option gives you  no
limitations while trying the program, it is exactly equal  to
the  registered version. The downside is that it does  access
my  permission server to ask for permission to run each  time
Serv-U  is  started. This is how the 30 days of  try-out  are
enforced.

All  the æLogXXXXÆ entries switch logging options on or  off.
Their names say it all, so IÆll let you figure them out.

The   æRegistrationKeyÆ  entry  is  used  for  entering   the
registration  code. You get this code after registration.  By
default it has no value and for evaluation of the program  it
should be left blank or out of the .INI file.

æAnonRelPathsÆ  determines  if  anonymous  users  should   be
treated with all path names relative to their home directory.
This  is  desirable for use with WWW browsers that insist  on
having access to the root directory (æ/Æ). Switching this  on
limits  anonymous  users  to  the  sub-tree  of  their   home
directory, they cannot switch to other drives. If you  switch
it  off then anonymous users will be treated like all others.
Default is switched on.

The  next  entry is æWindowÆ and this is set by Serv-U  every
time  the  program is stopped. It contains the last  position
and   size   of   the   program   window,   in   the   format
ætop,left,width,heightÆ. Likewise,  æUserInfoWinÆ  saves  the
window position of the user information window, in the format
ætop,leftÆ.

To  enable  directory change messages you  have  to  set  the
æDirChangeMesFileÆ entry to a valid file name. This can be  a
complete  path  name, in which case the  same  file  will  be
displayed  for  all path changes, or it can be  a  file  name
only, which means Serv-U will look for that file in the  path
the user is changing to.

If  links  should be available and displayed  in  the  userÆs
directory listings then æLinkFileÆ should be
set to the file name to use. The file name format is the same
as for æDirChangeMesFileÆ.

To  check if anonymous æpasswordsÆ resemble an E-mail address
you can set æCheckAnonPassÆ to YES, ON or TRUE. Likewise, you
can  switch checks off by setting it to FALSE, NO or OFF, and
this  is  also  the default. In that case Serv-U  will  allow
anything as an anonymous password.

Finally, æVersionÆ keeps track of the Serv-U version  number.
Format is æmajor,minor,revision,build no.Æ and it is used for
automatic .ini file conversion.

[SIGNONOFF]
This section contains the messages that are displayed after a
user  contacts the FTP server and just before he disconnects.
Every  line  has a separate entry with a number at  the  end,
denoting  the order. The sign-on message is put in æSignOnxxÆ
entries  (with xx the line number), and the sign-off  message
is put in æSignOffxxÆ.

There  are  several special character combinations recognized
by Serv-U and they are expanded to their actual values when a
user logs on or off. They all begin with æ%Æ and you can find
a  complete  list in the æHow to use sign-on and/or  sign-off
messagesÆ section.

A tip: Keep the number of lines and the their length limited.
Most  FTP clients will mess up lines over 80 characters,  and
since  a  FTP reply code is tagged to the beginning of  these
lines  before they are sent, it is wise to keep them to  less
then 75 characters.

[IP-ACCESS]
This  section  determines  which client  IP-numbers  will  be
allowed access to Serv-U. There are two kinds of rules: Those
that refuse access in the form of æBounceÆ entries, and those
that  grant  access using æAllowÆ entries.  If  this  section
doesnÆt exist, or no entries are found, then all clients  are
allowed  to contact the server. The reverse is also true,  if
there is even a single entry (æBounceÆ or æAllowÆ) then  only
those clients will be allowed to contact the server that pass
the  rule.  All entries are numbered sequentially  (æAllow1Æ,
æAllow2Æ  etc.)  and  they are evaluated according  to  their
number from first to last. Numbers should be consecutive. The
æBounceÆ rules are evaluated before the æAllowÆ rules.

The IP-number of the client is matched section by section  to
each rule until a match is found. If the matching rule is one
of  the æBounceÆ rules, the client is disconnected. If the IP
number matches an æAllowÆ rule then he can proceed. The rules
can be exact IP-numbers, or contain special characters. There
are two of those:

     *    = wildcard, match any number
     -    = denotes a range

A  quick example: The rule æ132.*.76.48-89Æ will allow  entry
to  clients with an IP-address starting with 132, the  second
section  can be anything (0..255), the third must be  76  and
the  last  section  should  be  between  48  and  89  (limits
included).

[USER=æNameÆ]
The  information  about  a user is stored  in  this  section,
æNameÆ  stands for the userÆs name. Each user has a  separate
section.  It  contains information needed to  authenticate  a
user  during login, and rules determining what this  user  is
allowed  to access. The Serv-U program will first check  this
section  for a regular user. If no applicable information  is
found  and  the  user is a member of a group,  the  group  is
addressed for the same information. If the result of this  is
still undetermined, the special user name æALLÆ is searched.

Now  to  the  entries that can be found in this section.  The
identity  of  a  user is verified by comparing his  password,
after  encryption, with the one in the æPasswordÆ entry.  The
UNIX  æcrypt()Æ command is used to encode the passwords. This
makes  it possible to extract users with their password  from
the  PASSWD file of a UNIX system, the same passwords  should
work  on  both systems. Unfortunately, there is not a  single
standard for password encryption on UNIX systems these  days.
Serv-U  uses the most common scheme, but this might not  work
for your system.

If  the  password matches, the home directory of the user  is
taken from the æHomeDirÆ entry. This should always be a  full
path name, including drive letter!

To make a user a member of a certain group, the æGroupÆ entry
can  be  used.  All information needed and not found  in  the
userÆs section; password, home dir and file/directory access,
are then  looked for in the groupÆs section.

Information  about file and directory access for  a  user  is
stored  in  the æAccessÆ entries. Each of these is  numbered,
and  access information is checked in order: first  comparing
it  to  the  first rule, then the second, etc. The  numbering
must  be consecutive. Access rules start with a path or  file
name.  These  paths are usually full names,  including  drive
letter.  If  the drive letter is missing, they apply  to  all
drives.  If different settings are needed for a subdirectory,
then  a  rule  with that directory should appear  before  its
parent,  i.e. with a lesser number (As a consequence  of  the
order in which Serv-U evaluates access rules). The path in an
access rule is followed by a comma and the access information
itself.  This  can be a combination of up to eight  different
characters:

     R    = read access to files
     W    = write access to files
     M    = modify access to files (implies write access)
     E    = execute access, for remotely starting programs
     C    = right to create subdirectories
     D    = right to delete subdirectories
     L    = directory list access
     P    = the rule æpropagatesÆ to sub directories as well

It  is entirely possible to have no access information at all
(only  a  path). This means that the user will not  have  any
access  to  that  path. One thing to realize  is  that  write
access  to a file does not imply read access! As you can  see
it is also possible to specify access rights for the parallel
and  serial  ports.  They are part of  the  regular  security
scheme  and to transfer to or from a port a user needs access
rights.  Then  finally, the path in an access rule  does  not
have  to point to a directory. It is also possible to specify
a filename. Of course, the æCÆ, æDÆ, æLÆ, and æPÆ rights will
not have any meaning then.

There  are two special user names: æAnonymousÆ and æALLÆ.  If
there is an user æAnonymousÆ, it will be possible to log into
the  server without a password. Instead, Serv-U will ask  for
the  userÆs E-mail address and log this. Most of the  regular
entries apply for æAnonymousÆ as well, except æPasswordÆ  and
æGroupÆ, these are ignored. In fact, for anonymous users  the
sections for groups and æALLÆ are never searched.

The user æALLÆ is searched if no appropriate rule is found in
a  userÆs or the userÆs groupÆs entry. It can contain any  of
the regular entries.

The  æLoginMesFileÆ  entry is used for pointing  to  a  login
message file that should be displayed to the user upon login.
The  same file name rules apply as for the æDirChangeMesFileÆ
entry,  and you can find more details about its usage in  the
æHow to setup user specific long messagesÆ section.

The  user  heading  can contain an added æ@Æ  followed  by  a
number,  like æ[USER=Anonymous1@1]Æ. This indicates that  the
user name is associated with a particular IP number for multi-
homed IP support. A list with IP numbers and their index  can
be found in the æ[IP-HOMES]Æ section.

[GROUP=æNameÆ]
These  sections contain the group info. The entries here  are
exactly the same as those for a user, except that the æGroupÆ
entry has no meaning of course.

[IP-HOMES]
This section lists all the IP numbers that Serv-U should  use
for multi-homed IP support. Each line couples an index number
with    a    corresponding   IP   number    of    the    form
æIPx=yyy.yyy.yyy.yyyÆ. In this æxÆ is the index  number  (any
positive  number between 1 and 30000), and æyyy. . .Æ is  the  IP
number that should be associated with it.

When  a user name should be coupled to a particular IP  home,
the  index  number for that IP home is appended to  the  user
name, preceded by a æ@Æ character.

[EXTERNAL]
This  heading denotes a list of dynamic link libraries  which
Serv-U  should  use to very user access. In case  the  Serv-U
user  database does not provide an answer to access  requests
the  inquiry  is passed on to the first DLL in the  list,  if
this  DLL  does not have an answer it is send to  the  second
DLL, and so on.

Each   line  in  this  section  has  entries  of   the   form
æClientCheckDLLÆ. These are followed by an order  number  and
specify the file name of the DLL to use. The DLL file  should
be  either in the Serv-U program directory, somewhere in  the
DOS path, or in the Windows directory for Serv-U to find it.

3.3 Using External User Access Verification DLLs
------------------------------------------------

Serv-U  can  use an external DLL to verify client access  and
retrieve information like a client's home directory  etc.  If
one  of  more  external DLLs are specified and Serv-U  cannot
find  the appropriate information internally it will question
each  of  the  external DLL's in turn. This can  be  used  to
create  an  interface to external user databases,  which  can
then  control FTP access. If the appropriate DLL exists,  for
example  the NT build-in user database could be  used,  or  a
Novell user database.

Setup
-----
To   make   Serv-U  use  external  DLLs  for  client   access
verification you need to add the DLL names to the  SERV-U.INI
file. At the moment there is no interactive user setup to  do
this, so the ini file has to be edited directly. There can be
more  than  one DLL, and Serv-U will query them in the  order
specified  until  one of the DLLs signals  that  it  had  the
required information.

The   DLL  names  need  to  be  added  to  a  section   named
'[EXTERNAL]'. The format is as follows (for example):

     [EXTERNAL]
     ClientCheckDLL1=CHKNOVELL.DLL
     ClientCheckDLL2=CHKNT.DLL
            .
            .

The  file names can be either full path names, or file  names
only.  If  the full path is specified then Serv-U  will  only
look at that path. If only the file name is given Serv-U will
first  look  in  the  program  directory,  then  the  current
directory,  the  entire  PATH, and  finally  in  the  Windows
directories.

DLL Specifications
------------------
The  DLL  entry  point for Serv-U needs to be  the  following
function:

     int HandleClientEvent(RClientEventStr* pEventStruc)

Please note that the function name is case sensitive!
The  function should return TRUE (=1) if it handled the event
and  does  not  want it to be passed on to the next  DLL.  It
should return FALSE (=0) in case it didn't handle the event.

The RClientEventStr structure is defined as follows:

     struct RClientEventStr {
       int Event;        // event code
       int  Flag;        // flag, meaning depends  on event
       char User[40];    // user name
       char  Aux[512];   //  auxiliary  area,  usage depends on event
       char HostIP[16];  // server IP home
     }

The 'Event' code determines the nature of the request and can
have the following values:

     #define SRVU_LoginMesFile    1    // get login message file
     #define SRVU_HomeDir         2    // get home dir
     #define SRVU_Password        3    // verify password
     #define SRVU_IPAccess        4    // verify IP access
     #define SRVU_WriteFile       5    // verify write access
     #define SRVU_ReadFile        6    // verify read access
     #define SRVU_ModifyFile      7    // verify mod./del. file access
     #define SRVU_ExecProg        8    //  verify  execute access
     #define SRVU_ListDir         9    // verify dir listing access
     #define SRVU_ChangeDir       10   // verify dir change access
     #define SRVU_DeleteDir       11   // verify dir delete access
     #define SRVU_CreateDir       12   // verify dir create access


Event Details
-------------
SRVU_LoginMesFile
       On entry:    User = user name
       On return:   Flag = TRUE (=1) if file name was found,
                           FALSE (=0) otherwise
                     Aux = file name of login message file, if one  was
                           found

SRVU_HomeDir
       On entry:    User = user name
       On return:   Flag = TRUE if home dir was found, FALSE
                           otherwise
                     Aux = home dir (full path), if one was found

       Note:        In case a user account is disabled 'no  home
                    dir' should be returned.

SRVU_Password
       On entry:    User = user name
                     Aux = password the user entered
       On  return:  Flag = TRUE if password  was  correct,
                           FALSE otherwise

SRVU_IPAccess
       On entry:    User = user name if available
                     Aux = IP address of client, in text format
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

       Note: If no user name is present it means the client
             just connected and a check should be made  for  server-
             wide IP access. If a user name is present access should  be
             checked for that particular user only.

SRVU_WriteFile
       On entry:    User = user name
                     Aux = full path of file
       On return:   Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_ReadFile
       On entry:    User = user name
                    Aux  = full path of file
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_ModifyFile
       On entry:    User = user name
                     Aux = full path of file
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_ExecProg
       On entry:    User = user name
                     Aux = full path of program name to be executed
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_ListDir
       On entry:    User = user name
                     Aux = full path of directory
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_ChangeDir
       On entry:    User = user name
                     Aux = full path of directory
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_DeleteDir
       On entry:    User = user name
                     Aux = full path of directory
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise

SRVU_CreateDir
       On entry:    User = user name
                     Aux = full path of directory
       On  return:  Flag = TRUE if access is allowed, FALSE
                           otherwise


4. Getting In Touch - Bugs & Registration
=========================================

If  you  have questions or want to offer suggestions you  are
most  welcome  to drop me a line. However, please  check  out
this  manual and the Cat Soft Web site first to  see  if  the
answer to your question is already in there. Although I truly
love  to  hear  from  you and will do my best  to  help,  the
problem  is  that each day between 30 and 50 E-mail  messages
arrive  here,  and  you are talking to a one-man,  spare-time
company!  As it is IÆm spending  2-3 hours a day on answering
E-mail  and  that is about as much as I have  to  spare.  The
easiest  way  to  get  in touch with me is  via  E-mail.  The
address is:

     [e-mail]

The Cat Soft Web site can be found at:

     http://www.cat-soft.com

Regular  mail  should  work as well, but  might  take  a  bit
longer. My address for this is:

     Rob Beckers
     210 Alexander Ave., Apt. D
     Durham, NC 27705
     USA


4.1 Serv-U Mailing List and Conference
--------------------------------------

There is also a WWW conference for Serv-U, and a mailing list
where  you  can  ask  questions and  discuss  Serv-U  related
topics. To subscribe to the Serv-U mailing list, send  an  E-
mail message to:

     [e-mail]

with  only  a  single line in the message body, which  should
read:

     subscribe Serv-U

This  will  return a message from the list manager  within  a
minute  or  so, explaining in detail how to post messages  to
the  list and related matters. I am also subscribed  to  this
list,  so each message you post will reach my E-mail  box  as
well.  When needed IÆll respond to your message, but my  hope
is  that others will reply to, thus cutting down a bit on the
flood of messages I have to answer each day.

For the WWW based Serv-U conference, take a look at:

     http://www.spring.com/yapp-bin/public/read/apps/58

4.2 Reporting Bugs
------------------

Nothing  in  this world is perfect, least of  all  me!  Alas,
chances are that despite careful testing youÆll still find  a
bug.  Please donÆt think others will report it, let me  know!
There  are  a few things I need to know in order  to  improve
chances of fixing the beastie, so take note of the following:

   ╖ Most  important: Can you get the same bug  to  appear  by
     repeating  certain actions? Please try hard;  without  a
     recipe  for repeating a bug, itÆs going to be very  hard
     to track it down.
   ╖ What  TCP/IP  and WinSock stack are you using? Brand/type
     and  version  number please. What operating system  (DOS
     version  and Windows or Windows-For-Workgroups,  Windows
     95,  NT  version x.xx)? Any memory manager (QEMM  etc.),
     what version?
   ╖ Please  indicate also if this bug is merely  cosmetic  or
     of  vital  importance  for using  Serv-U.  Somewhere  in
     between  is  possible as well of course. By the  way,  I
     consider security related bugs very important!
   ╖ Finally,  please give me a chance to fix  a  bug,  before
     you  start to shout all over the Internet how  bad  this
     program is . . .

4.3 Registering Serv-U
----------------------

If  youÆre happy with the performance of Serv-U, then  please
make me happy and register this program! Just a few words for
those  who  are in doubt: Making this program took  me  (very
literally)  months  of work, spread out  over  the  last  two
years.  Your  registration fee is going  to  motivate  me  to
continue  improving  Serv-U.  In  general,  registration   is
important  for shareware programs: It makes it  possible  for
you to use professional quality software for peanuts. Lastly,
being  a  biomedical engineering graduate  student,  IÆm  not
exactly making lots of $$Æs (to put it mildly). So, those  25
bucks for registration mean a lot to me!

What  do  you  get if you register? As soon  as  I  get  your
registration   IÆll  send  you  a  registration   code   plus
instructions  on  how  to add it to the  program.  This  will
enable  you  to  use  the program after the  30  day  try-out
period. Please let me know your E-mail address, since  Serv-U
is  tailored to pick the registration key out of  the  E-mail
message  I will send you. In case I have your E-mail  address
youÆll  also  get  notified  when  there  are  updates.  Once
registered  youÆll get those updates for free. That  is,  you
can use the same registration code on the updates, but youÆll
have  to  get them yourself. Apart from all this youÆll  also
get the nice, warm feeling of having contributed to improving
my earthly wealth!

The  registration code is tied to the user/company  name  you
specify on the registration form. You can see if your  server
is  registered  by  looking  at  the  æAboutÆ  dialogbox:  If
registered it will tell you to whom. Another thing to keep in
mind is that the registration information is sent back to any
FTP  client who uses the FTP command æHELPÆ. This  is  not  a
much  used command but in principle it allows the whole world
to  find out who paid for your copy of Serv-U. If youÆre  the
lawful  owner  of  the  server  this shouldnÆt bother you, if
not. . .

The  registration fee is $25 for each copy. If  you  want  to
make  me  even happier and need several copies, the following
license prices apply:

     The FTP Serv-U license prices:

     1-9  $25 per copy

     License for:
     20   $250
     50   $500
     100  $700
     100+ $500 per block of 100 copies

     Licenses for more than 500 copies are negotiable.
     Educational discount: For licenses of 50 or more copies:
     30% discount.

The  ænumber of copiesÆ in the above refers to the number  of
concurrently  running Serv-U FTP servers in your organization
(i.e.  it  is  independent of the number  of  concurrent  FTP
clients).  The  last page of this manual is the  registration
form. Please use this form for all registrations! That way  I
can keep my administration manageable.

4.4 Registration in the US
--------------------------

To   register  from  within  the  US,  please  fill  out  the
registration  form  and send it along  with  payment  to  the
address  on  the  form. A (personal) check made  out  to  Rob
Beckers is the preferred form of payment, but a Postal  Money
Order,  or  Purchase  Order is welcome too.  If  you  need  a
receipt,  then  please mention this on the registration  form
and I will send you one by paper mail. It is also possible to
register via CompuServe's SWREG service. The registration  ID
for  that  is  7743 and this costs $30 (Since CS  takes  $5).
Sorry,  but  I  cannot accept credit cards  at  this  moment.
However,  I  am working on this and hope to be able  to  take
credit  cards  soon. Drop me a line for the  latest  info  on
this.

                       Important Note:
                       ===============
Make sure to include the registration form with whatever you
  send me!! IÆm receiving way too many checks and purchase
orders without a form, often even without a name nor a phone
 number. If your order goes through a purchasing department
then please make sure they include the registration form with
                      the PO or check!


4.5 Registration from Abroad
----------------------------

While  borders are disappearing in many parts of  the  world,
getting  money across from one  country to another  is  still
not  easy, at least not when you want to keep the cost  down.
Below is a list of payment options that I accept (in order of
preference).  Please  make sure to include  the  registration
form  with anything you send me. Sorry, but no credit  cards!
Instead, these are the payment options:

     ╖ Using CompuServe's SWREG service. The registration ID
       for Serv-U is 7743 and registration costs $30 this way (CS
       takes $5, so I end up with $25).
     ╖ By check, drawn at an American bank and in US dollars.
       The check should be made out to Rob Beckers.
     ╖ By American Express Travelers Checks for the correct
       amount in US dollars. These are cheap and safe, but there
       might be a minimum commission charged by your bank. The
       checks should be made out to Rob Beckers and don't forget to
       sign them twice!
     ╖ By Postal Money Order. As I understand it, you can buy
       these international money orders in most countries for very
       little money ($3 here in the US). Payment is in your own
       currency, but the money order should be made out for US $25
       and to Rob Beckers.
     ╖ By cash, but only in US dollars and I give no guarantees
       about safe arrival! Please do not send me other currencies,
       it would probably cost me much more to convert them to US
       dollars than it will cost you. A trick I found useful for
       sending cash in envelopes: put the money in a folded sheet of
       paper so it doesn't shine through the envelope. This might
       improves chances of arrival considerably.
     ╖ For Europeans: It is possible to pay using a Euro-
       Cheque. Make the check out for 40 Dutch guilders, i.e. write
       "DFL 40" for the currency. Don't forget to add the security
       number at the back. Send it to: Rob Beckers; St. Agnesstraat
       16; 6241CB Bunde; The Netherlands. Please send or E-mail the
       registration form to me in the US.
     ╖ For the Dutch: Het is ook mogelijk te betalen door fl.
       40 over te maken op girorekening 53.95.461 t.n.v. Rob Beckers
       te Bunde. Stuur dan wel even het registratie formulier per E-
       mail naar mij toe. S.v.p. geen geld vanuit Belgie of
       Duitsland rechtstreeks overmaken, want daarvan blijft
       niet veel over!
     ╖ For Canadians only: By any type of (personal) bank check
       of Canada. Just make the check out in US dollars. Doing so is
       easy: Write "US" in front of the dollar sign and add "US
       Funds" below the sum. This way neither of us pays anything
       extra (I don't, and as far as I know you don't either, but
       check with your bank if you want to make sure). The check
       should be made out to Rob Beckers.
     ╖ By direct money transfer in US dollars to my American
       bank account. Please add $13 extra, since that is the fee my
       bank charges me to receive money this way. Please send me the
       registration form by E-mail in this case. The details for a
       wire transfer are:

          Bank:
               Wachovia
               Durham - North Carolina
          ABA/Routing no:
               053100494
          Account:
               No. 2373193064
               Rob Beckers
               210 Alexander Ave., Apt. D
               Durham, NC 27705
               USA



******************** REGISTRATION FORM **********************

ROB BECKERS
210 Alexander Ave., Apt. D
Durham, NC 27705
U.S.A.



                     REGISTRATION FORM SERV-U
                     ========================


           Name: ............................................

   Company Name: ............................................

        Address: ............................................

                 ............................................

                 ............................................

   Phone Number: ............................................

 E-Mail Address: ............................................
                  (Important! Reg. Code is sent by E-mail)
  No. of copies: .........

Additional comments, suggestions, complaints, praise, etc .

.............................................................

.............................................................

.............................................................

Registration fee is $25 per copy. Send this order form  along
with your payment to: Rob Beckers, 210 Alexander Ave. Apt. D,
Durham NC 27705, USA.

If   you  have any questions, comments or suggestions  please
contact  Rob  Beckers at the above address or via  e-mail  to
[e-mail]. Check out the site license prices in  the
manual if you need multiple copies.

As  this software is shareware it comes `as is', there is  no
warranty  implied  or  otherwise, nor  is  support  provided.
However, if you discover any bugs or problems please  contact
the developer at the above e-mail address.