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1991-11-13
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21KB
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408 lines
The WATTCP TELNET Server
by Erick Engelke
This program effectively allows you to remotely control your pc. There
is always work in place to improve TELNETD, work which is based on the
large amount of positive feedback from users like you. I post to
comp.protocols.tcp-ip.ibmpc whenever I make significant changes
or improvements to this program.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
WARNING - TELNETD offers some simple password security provisions but remember:
1. TELNETD gets the password from an unencrypted disk file
2. TELNETD stores the password in memory as plain-text
3. All TELNET protocols send the password over the network in
plaintext - it's trivial to read a password on networks such
as Ethernet.
The password protection is merely one step above no protection.
Do not leave important information accessible through TELNETD.
Change your password frequently and use mixed case and numbers
interspersed. Avoid single words, use combinations of words.
Do not use the same password for TELNETD as you would for your
system priviledged account. The maximum password length is
16 letters.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Installation
TELNETD.EXE uses the Waterloo TCP kernal to do all the network i/o.
Installing the program can be performed by simply editing the ASCII
configuration file named WATTCP.CFG. Try creating such a file with
information like the following and place it in the *SAME* subdirectory
as TELNETD.EXE.
---I:\NETWORK\WATTCP.CFG----------------------------------------------
my_ip=129.97.128.254 # substitute the PC's ip number
netmask=255.255.254.0 # substitute your local net mask
gateway=129.97.128.1 # substitute your local gateway
# the next lines are optional
telnetd.password=Time2Go # telnetd session password
telnetd.message="Wizbang Computer Network" # openning message
----------------------------------------------------------------------
You need not include quotes except if you wish to include
non-alphanumeric characters like '#',';' or spaces.
Full installation instructions for installing any Waterloo TCP
based program is available from sunee.uwaterloo.ca [129.97.128.196]
in pub/wattcp/apps.zip. If you end up having difficulty running
TELNETD, download that zip file, it will prove very useful. Also
included in that file is information on how to use BOOTP, multiple
gateways, and many other features.
The above type of configuration is useful in all WATTCP based programs,
but you can also add some special parameters which will only be
interpretted by specific WATTCP programs. In this case all parameters
specific to TELNETD are prepended with 'telnetd.' to make them
easily identifiable and to avoid naming conflicts with other WATTCP
applications.
Load (and configure) an Ethernet packet driver, then run TELNETD.
A message will appear indicating TELNETD is waiting for a caller and
it should report the correct IP address. An indication of a password
should appear for every time it encounterred a password in the
configuration process. If no packet driver is installed TELNETD will
have crashed by now.
Installing TELNETD on a Network
Do everything the same as above, but append the following line to
the WATTCP.CFG file:
include=?c:\telnetd.pas
and have user's place their private password in that file. Eg.
---C:\TELNETD.PAS-----------------------------------------------------
# joe's private config parameters
telnetd.message="Joe's Private Computer - KEEP OUT ALL SURF NAZIS"
telnetd.password=Knuths4thBook
----------------------------------------------------------------------
In the above example I assumed the 'c' disk was the local hard disk.
You could select the network disk or both. Here the network disk n:
has the last say on the password. The telnetd.password directive can
appear several times and in several files, but the last occurance
is the password actually used.
include=?c:\telnetd.pas
include=?n:\telnetd.pas
The question mark tells TELNETD to use the file if it exists but not
complain if it doesn't. You may like to leave a default password in
the WATTCP.CFG file, just so intruders are less likely to break in.
There are some other parameters which are sometimes good to set.
One which can enhance security is the inactivity timeout. Setting
this value to a non-zero value tells WATTCP to hang up the connection
if no activity occurs for a certain period of time. A good value
would be something like twenty minutes. Smaller values can be
-- WATTCP.CFG --------------------------------------------------------
# assuming properly configured as described earlier
# print a message for local user
print="Press control-break to get out of this thing"
# set the inactivity timeout value
inactive=1200 # 20 minutes ( 20 min x 60 sec/min = 1200 seconds )
----------------------------------------------------------------------
Using TELNETD
Go to a second PC. Using Clarkson University (CUTCP) TELNET, telnet
to the first PC. You could use NOS (KA9Q), but I don't think NOS
handles VT100 cursor keys and you will definately want them!
Other tested telnets include MicroVaxen, RS/6000 using AIX and
Macintoshes using MACTCP
When you TELNET to TELNETD, you may have to hit return. It's one
of those things left to fix. Sorry, but it's getting too late
tonight. You will then be confronted with a login message (from the
wattcp.cfg file) and a password prompt (if you selected a password in
the configuration file - otherwise skip this paragraph). You must
enter the password correctly within a reasonable number of tries or
TELNETD will complain and close the session. You must also reply
within a reasonable time limit.
The passwords can be almost any printable ascii string up to 16
letters. If you use characters other than alpha-numerics, you
should surround the password with quotes in the WATTCP.CFG file.
WATTCP removes the quotes when it parses the file, so you don't
enter the quotes when you enter the password at the prompt.
Assuming you passed the password test, TELNETD becomes a TSR and almost
immediately you will be at the DOS prompt. You are now logged in.
Anything you type on the remote PC will appear to be typed on the
TELNETD PC. QEDIT, LIST.COM, BORLAND C++, and many other programs
are compatible (check out the character translation). There will be
slight periodic delays. Using a 386 to run TELNETD will improve
your performance. If the screen appears to be messed up or incomplete,
you can have TELNETD redraw it by typing ESC R on the keyboard.
This usually happens from either a lost packet or contention on
the network card if you are using the same card for network disk i/o.
For example, if I am compiling then TELNETD can find very few
cracks in the network i/o because my computer is diskless. But most
operations are not so incredibly disk intensive and it feels quite
reasonable.
Remember that the remote PC is running VT 100 emulation and so