GRIPS 2: Government Rast…rocessing Software & Data/GRIPS_2.cdr/dos/ncsa_tel/pc_2_2_d.asc

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NCSA Telnet for the PC
Version 2.2
July 1988

(ASCII printable version of this document)
















UD-99
US-14



NCSA Telnet Version 2.2 source code and documentation are in the public domain.
Specifically, we give to the public domain all rights for future licensing of
the source code, all resale rights, and all publishing rights.

We ask, but do not require, that the following message be included in all
derived works:

Portions developed by the National Center for Supercomputing
Applications at the University of Illinois at Urbana-Champaign.



PROBLEM REPORTS

Mail all suggestions and manual corrections to:
NCSA Documentation and Publications Department
152 Computing Applications Building
605 E. Springfield Ave.
Champaign, Illinois 61820




DISCLAIMER

THE UNIVERSITY OF ILLINOIS GIVES NO WARRANTY, EXPRESS OR IMPLIED, FOR THE
SOFTWARE AND/OR DOCUMENTATION PROVIDED, INCLUDING, WITHOUT LIMITATION, WARRANTY
OF MERCHANTABILITY AND WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE.


TRADEMARK ACKNOWLEDGMENTS

PostScript is a registered trademark of Adobe Systems Inc.
UNIX is a registered trademark of AT&T.
SideKick is a registered trademark of Borland International Inc.
VAX, VMS, and VT102 are registered trademarks of Digital Equipment Corporation.
Hercules is a trademark of Hercules Computer Technology.
Enhanced Graphics Adapter, IBM PC, PC/AT, PC-DOS, Personal System/2, and
Topview are registered trademarks of International Business Machines
Corporation.
Microsoft Windows and MS-DOS are registered trademarks of Microsoft
Corporation.
Revolution 512 is a trademark of Number Nine Computer.
Tektronix 4010 and Tektronix 4014 are trademarks of Tektronix Corporation.
NIC is a trademark of Ungermann-Bass.
EtherCard PLUS is a trademark of Western Digital Corporation.
Ethernet is a trademark of Xerox Corporation.
3COM and Etherlink are trademarks of 3COM Corporation.







INTRODUCTION



PURPOSE OF NCSA TELNET


NCSA Telnet Version 2.2 for the PC provides interactive access
from an IBM PC or compatible to telnet hosts on TCP/IP networks.
NCSA Telnet is an implementation of DARPA standard telnet with
added features that take advantage of the local processing power
of the PC.



SPECIAL FEATURES


Special features of NCSA Telnet for the PC include:

%    VT102 emulation
%    Simultaneous logon to a number of computers
%    Ability to capture text to the PC disk or printer
%    File transfer server (standard FTP)
%    Remote copy server (rcp) for use with UNIX hosts
%    Ability to take full advantage of PC colors
%    Topview/Windows compatible mode
%    Tektronix 4014 emulation
%    Domain name lookup
%    Optional use of RARP for determining PC's IP address
%    Scrollback




SYSTEM REQUIREMENTS


To use NCSA Telnet you must have the following hardware:

%    IBM PC, PC/XT, PC/AT, IBM PS/2 model 30, or "true" compatible
    computer with one of the following Ethernet adapter boards:
    3COM 3C501 Etherlink
    MICOM NI5210
    Ungermann-Bass PC-NIC (same as IBM Baseband Adapter)
    Western Digital WD8003E EtherCard PLUS

%    or IBM PS/2 models 50,60 or 80, or "true" compatible computer
    with one of the following Ethernet adapter boards:
    Ungermann-Bass NICps/2
    3COM 3C523 Etherlink/MC

%    384K minimum memory

%    Ethernet or Thin Ethernet to connect the PC and other computers

To use NCSA Telnet you must have the following software:

%    PC-DOS or MS-DOS Version 2.0 or later.
%    A standard text editor will be helpful when editing the
    configuration file.



ABOUT THIS MANUAL


This section describes the organization of this manual, and the
conventions and nomenclature used in developing it.


Organization of This Manual

This manual is organized into six chapters. Each page of each
chapter is given a unique number that consists of the chapter
number, a period, and the number of that individual page
(beginning with the first page of the chapter). For example, page
2.3 is the third page of the second chapter. Each chapter is
divided into sections, and most sections are divided into
subsections.



Manual Contents

This manual is organized into the following chapters:

Chapter 1, "Starting and Quitting NCSA Telnet," describes how to
start NCSA Telnet and how to open and close a connection between
your PC and one remote host.

Chapter 2, "Introduction to Managing Sessions," introduces NCSA
Telnet's capability for multiple connections.  It also discusses
standard VT102 key emulation, keys used for common EDT operations,
and using a capture file.

Chapter 3, "More about Managing Sessions," discusses multiple
sessions in detail.  The Parameters menu options, DOS shell
feature, and several advanced functions are also described.

Chapter 4, "File Transfer," outlines procedures for transferring
files between a PC and a telnet host.

Chapter 5, "Tektronix 4014 Emulation," discusses NCSA Telnet's
ability to emulate a Tektronix 4014 graphics terminal.

Chapter 6, "Installation and Configuration," contains information
for system administrators (and other experienced users) to use
when installing and customizing a system.

Appendix A, "Error Conditions," describes some of NCSA Telnet's
error messages, as well as their causes and solutions.

Appendix B, "NCSA Telnet Command Reference," lists commands
available from the PC keyboard.

Appendix C, "Configuration File Summary," lists the keywords for
configuration file parameters.


Notational Conventions in This Manual

Figure I.1 shows some typical screen/user interactions using the
conventions employed in this manual. Those conventions, and
others, are explained here.

C:\> telnet machinename [machinename...]

National Center for Supercomputing Applications
NCSA Telnet for the PC version 2.2
(c) Copyright 1987,1988 Board of Trustees of the University of Illinois

ALT-H presents a summary of special keys



4.2 BSD UNIX (newton)

login:

Figure I.1.  Example of Notational Conventions


dothis        Information shown in courier boldface type represents
user entries.

ALT-key        Press and hold the ALT key and then press the key
designated by key. Then release both keys at the same
time.

variable    Do not enter the actual characters shown. Command line
characters shown in lowercase courier bold italic type
represent an entry that may consist of different
characters every time you make the entry. In other
words, it is a variable entry. If it indicates a
machine response, it means the actual wording of the
response will vary, depending on the filename,
machinename, and so on.

...        Do not enter an ellipsis. The ellipsis indicates that
you may enter more material similar to the material
preceding the ellipsis.

[ ]        Do not enter square brackets. Material or actions
presented between square brackets is optional and
should be entered only in certain cases.



INSTALLATION NOTE


This manual assumes that NCSA Telnet has been installed on your
system by a system or network administrator who has assigned an IP
address to your PC. Chapter 6 contains information to be used by
system administrators and other experienced users to install and
customize NCSA Telnet.






CHAPTER 1

STARTING AND QUITTING NCSA TELNET



CHAPTER OVERVIEW


This chapter describes how to start NCSA Telnet and how to open
and close a connection between your PC and one remote host. NCSA
Telnet also features multiple-session capabilities. If you want to
use more than one login session simultaneously, see Chapter 2,
"Introduction to Managing Sessions." Also see Chapter 2 for
information on how NCSA Telnet emulates a VT102 keyboard.



STARTING THE PROGRAM


To run NCSA Telnet from the PC command line, from any
subdirectory, enter:

C:\ > telnet machinename

This initiates a connection to the remote computer with the name
given as the machinename parameter. Normally the host machine
immediately prompts you for a login name and password to begin the
session.


Setting the Terminal Type

NCSA Telnet emulates a VT102 terminal. When you log in to a host,
the host operating system does not know what type of terminal you
are using. Consult the operating system manual for how to set
terminal type and try setting it to VT100 or VT102. For systems
that do not support VT102 (such as many UNIX systems), use VT100,
which is compatible with VT102 emulators. These examples show how
to set the terminal type for two popular operating systems, UNIX
(using the C shell) and VAX/VMS.

newton% set term=vt100;tset        For UNIX hosts.

B$ SET TERM/INQ                For VAX/VMS hosts.

THE HELP SCREEN


For a command summary, press ALT-H. A one-screen summary of
command keys appears, as shown in Figure 1.1. The online help
summary serves as your quick reference to the command keys.

Keyboard usage for NCSA telnet:

Alt-A     add a session                    Alt-Y     Interrupt Process
Alt-N     next session                     Alt-O     Abort Output
Alt-M     message screen                   Alt-Q     Are you there?
Alt-E     escape to DOS shell              Alt-U     Erase line
Alt-G     graphics menu                    Alt-K     Erase Kharacter
Alt-C     toggle capture on/off            Alt-X     close connection
Alt-R     reset VT102 screen               HOME      exit graphics mode
Alt-H     this help screen                 Ctrl-HOME clear/enter graphics mode
ScrLock   pause/restart screen (DO NOT use Ctrl-NumLock)
ScrLock   enter/exit scroll-back mode
Alt-T     start file transfer as if typed: ftp [internet address]
Alt-I     send my internet address to host as if typed
Alt-S     skip scrolling, jump ahead
Alt-P     change a parameter, one of:
          color, capture file name, backspace, session name, screen mode
Alt-F3    abort program completely.  STRONGLY discouraged


Press ESC for information page, space bar to return to session:

Figure 1.1.  NCSA Telnet Help Screen




QUITTING NCSA TELNET


To exit the program, log out of the host machine using the
appropriate logout procedure for that machine. If you have
concurrent sessions with more than one machine, you must log out
of each machine. Then NCSA Telnet exits and the DOS prompt is
displayed.

If one of the hosts crashes, or a session is otherwise hung up,
press ALT-X. NCSA Telnet will first prompt you for confirmation
and then attempt to close the session while preserving your other
live sessions.

When all else fails, and it appears that all of the connections
are completely jammed, press ALT-F3 to abort the program.  Only
use ALT-F3 as a last resort.


CTRL-C Will Not Exit

Pressing CTRL-C or CTRL-BREAK will send a CTRL-C to the host.
These commands cannot be used to break out of NCSA Telnet, and
they will not end your session.








CHAPTER 2

INTRODUCTION TO MANAGING SESSIONS



CHAPTER OVERVIEW


This chapter introduces NCSA Telnet's capability for multiple
connections with one or more hosts. The chapter describes standard
VT102 key emulation, keys for some common EDT operations, how to
work with multiple sessions, and operations with the capture file.



KEYBOARD USAGE


When NCSA Telnet is running, the PC appears to the host as a VT102
terminal. For keys that the PC keyboard and the VT102 keyboard
have in common, NCSA Telnet transmits the keystrokes unmodified.
The VT102 keyboard has some keys that the PC keyboard does not
have, and treats other keys differently. Many VT102 keys have
special meanings when they are transferred to the host. To provide
full VT102 functionality, some PC keys are used to emulate the
operation of VT102 keys.

Table 2.1 lists the PC keys to use for VT102 terminal emulation.

Table 2.1.  PC Keys Used for VT102 Terminal Emulation

To Send a VT102 Code            Press PC Key(s)

RETURN                    ENTER

DELETE                     BACKSPACE

BACKSPACE                 CTRL-BACKSPACE

LINE FEED                CTRL-ENTER

Keypad ENTER                 F10
(not identical to RETURN)

Keypad . (decimal point)        DEL

Keypad - (hyphen)            F5

Keypad , (comma)            F6

Keypad 0                 INS

Keypad 0 to 9                ALT-0 to ALT-9

-, /, ,, .                -, /, ,, .

PF1 to PF4                F1 to F4

     See Chapter 3 and Chapter 6 for information on how to switch the
designations of these keys.


VT102 Functions for the EDT Editor

Table 2.2 lists some VT102 terminal emulation functions that help
users who are working with the EDT editor under VAX/VMS.

WARNING: If you are not using the EDT editor, ignore the use of
these keys. They produce unpredictable results on other systems.

Table 2.2.  VT102 Functions for the EDT Editor

For the EDT Operation            Press PC Key(s)

Save-and-exit                F9

Select                    F7

Cut                    F8

Paste                    F1,then F8

Cursor to beginning of this line    HOME

Cursor to end of this line        END

Scroll backward one screen        PG UP

Scroll forward one screen        PG DN

Return to the previous formfeed        CTRL-PG UP

Go to the next formfeed            CTRL-PG DN

EDT help screen                F2



MULTIPLE SESSIONS


When you first run NCSA Telnet, you can start up multiple sessions
with a single command.

C:\> telnet machinename [machinename ...]

Even if you do not choose multiple sessions when you first run
NCSA Telnet, you can later add sessions, as described in the
following paragraph.


Using ALT-A to Open Another Session

When you have opened a connection to a single host, you can open a
second connection, to that host or a different one. To do this,
press ALT-A (A for add). NCSA Telnet responds by prompting for
the name of a computer to which it should attempt a connection.


Indicating the Host

NCSA Telnet can only communicate with host computers that have IP
addresses. IP addresses can be looked up several different ways.

1.    Any name that is in the configuration file can be used.
(Your system administrator can tell you the names listed
there.)

2.    NCSA Telnet can be configured (by the system administrator)
to use the domain-based nameserver to look up host names. Any
name that can be resolved by the domain nameserver can be used.
An example is sri-nic.arpa.

3.    You can use the full Internet number of the machine, in
decimal, separated by periods, such as 192.17.22.20.

4.    If the machine is on the same Ethernet, you can enter a
pound sign (#), followed by the host number it uses on your
Ethernet. The host number is determined by the class of
addressing and the subnet mask (which your system administrator
can determine for you). For example, if your PC is host
192.17.22.20, you can access host 192.17.22.30 by entering #30
for the host address.


Response Time of the Host

NCSA Telnet attempts to make a login connection with the named
host. Usually the connection is instantaneous, and the host
machine prompts you for a login name immediately. However, the
connection attempt may take several seconds. Even after the telnet
connection has been completed, if a remote host is heavily loaded
it may take additional time (up to two minutes) to prompt you for
a login name.

When the connection is established, the asterisk (*) in the status
box for the connection will disappear or change to a small box. If
NCSA Telnet makes the connection, but the remote host does not let
you log in, you may want to press ALT-X to end the connection.


Using Scrollback Mode

The SCROLL LOCK key does double duty. It prevents the screen from
scrolling when new text arrives, and also puts you into scrollback
mode. In scrollback mode, the up and down arrow keys and PG UP and
PG DN scroll the screen backwards and forwards. When you press the
SCROLL LOCK key again, it ends scrollback mode and resets the
working area of the screen.

The number of lines that are saved is limited by the amount of
memory in your machine and is set in the configuration file. If
your PC runs out of memory, or the specified number of lines have
already been stored, it will start wrapping the scrollback around.

NOTE:  No other commands work while you are using scrollback
mode.


The Status Line

Only 24 lines are needed for VT102 terminal emulation, so line 25
on your PC screen is used to indicate the connection status of
your terminal sessions. For each host you are connected to, a
session name appears in reverse video. The name in the lower left
corner of the screen is the current session. Beside each name is a
status box that indicates various attributes of a session:

(gray)        Connection is established, waiting
(small box)    Active connection, always in lower left corner
*        Connection pending, trying to connect to host
/ or \        Text has been written to this invisible session


Switching Between Sessions (ALT-N)

The status line at the bottom of the screen indicates the active
telnet sessions. To rotate to the next session, press ALT-N (for
next). This action makes the next session the current one and
moves its name to the lower left corner of the screen. The screen
image for this session is now displayed, and you should be ready
to proceed. Characters typed at the keyboard are always sent to
the current session.


Displaying Console Messages (ALT-M)

In the process of connecting and communicating with other hosts
via TCP/IP, NCSA Telnet provides you with information on the
console (message) screen. To see this screen, press ALT-M. When
you have viewed the messages, press any key to return to your
session. The information on the console screen can tell you about
errors, warnings, FTP access to your PC, and network conditions
that may be of concern to network administrators.


Exiting the Present Connection (ALT-X)

ALT-X initiates the close procedure for the current session.  To
prevent this from happening accidentally, NCSA Telnet prompts you
to confirm that the connection should be closed.   After
confirmation, the connection shuts down.  The close may take
several seconds to complete.

NOTE:  You can press ALT-X to log out of a host as well as
terminate a given session, but it bypasses normal conventions and
may cause problems for the host. The correct way to close a
connection with a host is to log out of the host using the normal
logout procedure for that host.



CAPTURE FILE OPERATIONS


Text that appears on the screen can be captured and sent to a file
or the local printer. When you press ALT-C, capture is turned on.
Pressing ALT-C again turns capture off. Any text that appears on
the screen is captured and appended to the capture file. NCSA
Telnet never erases the capture file, only appends text to it. The
default capture file is named capfile, but you can change that, as
discussed next.


Designating a Capture File

Designate a different capture file by using the Parameter menu.
When you press ALT-P the Parameter menu is displayed. (Most of
the Parameter menu choices are discussed in Chapter 3.) Use the
arrow keys to select the Parameter menu entry for the capture file
name.  Press RETURN to clear the current entry and then enter
your new file name. After the name of the capture file has been
changed, all subsequent ALT-C commands use the new capture file.
You can also change the name of the capture file "permanently" in
the configuration file (see Chapter 6).


Using PRN

If you want to send all captured text directly to a local printer,
use the filename prn as the designated capture file name. PC-DOS
reserves this filename for the printer.

A common problem can occur while you are capturing files to the
printer that can cause NCSA Telnet to abort. If the printer is
offline or out of paper when a capture begins, the message:

Error, A(bort) R(etry) or I(gnore)?

appears on the screen. At this point, turn on the printer and then
press R for retry. Do not press A at this point because it will
abort NCSA Telnet and cut off all of your network connections.


One Capture at a Time

You can capture text to a file or the printer in any session, but
not for more than one session at a time. When a capture is active
for a session in the background, you cannot invoke capture on the
current session. If you attempt to do so, you will not get the
confirmation message on line 25 and NCSA Telnet reminds you of the
error. The capture procedure will continue to capture all text for
the background session while you interact with the current
session.








CHAPTER 3

MORE ABOUT MANAGING SESSIONS



CHAPTER OVERVIEW


This chapter continues the discussion of multiple sessions and
describes more advanced aspects of the NCSA Telnet working
environment. The chapter explains how to reset the VT102 screen,
how to abort NCSA Telnet, the DOS shell feature, and Parameters
menu options.



KEYBOARD COMMANDS


Skip Command (ALT-S)

The skip command causes the screen to "skip ahead" over scrolling
text. The text is placed into the scrollback region, but the
screen update advances to the end of the local network buffer
instead of printing every line on the screen. The purpose of this
feature is to help you when you type a command which produces so
many lines of output that you don't want to wait for it to scroll
by. Press ALT-S and the screen will pause, then redraw at the end
of the local buffer. This won't solve all of the network buffering
problems for interactive use, but it should help. Capture to disk
and scrollback are not affected by skip.


Resetting the VT102 Screen (ALT-R)

ALT-R clears and resets all modes associated with the current
virtual VT102 screen. Some host programs can accidentally set
graphics mode on or fail to leave graphics mode. You press ALT-R
to override all VT102 mode settings. These include turning off
wrap mode, resetting graphics mode, setting the keypad mode back
to the default, and resetting tabs to every eight spaces. After
using ALT-R, you may wish to set your terminal type again to allow
the host to reset whatever VT102 modes it needs.


Aborting the Program (ALT-F3)

If for some reason none of the current connections respond, SCROLL
LOCK is not on, and ALT-R and ALT-X do not appear to have any
effect, ALT-F3 is a general abort command that exits NCSA Telnet
and returns you to DOS. If NCSA Telnet is aborted with ALT-F3, it
cannot notify the host(s) that your session(s) are terminated.
Your sessions are left in an undetermined state. This can cause a
variety of problems for the host, because it cannot immediately
determine that the session has ended. For example, you may have
programs which continue to run on the host, even though you exited
telnet with ALT-F3.


Escape to DOS Shell (ALT-E)

Pressing ALT-E to escape to DOS preserves your connections while
you use the DOS command shell. You may use most DOS commands and
programs, including those which look at directories, edit source
files, or even compile programs. To return to NCSA Telnet, you
must enter the command exit at the DOS prompt.

During the escape to DOS, NCSA Telnet is monitoring the Ethernet
for incoming packets every one-half second. If you run other
programs which affect the Ethernet or the timer which NCSA Telnet
uses, your connections may be lost or worse, your computer may
crash. The following programs are examples of those which
terminate the network handling of NCSA Telnet, causing connections
to be lost or DOS to crash:

%    SideKick (it turns off timer processes, so it can cause lost
connections)
%    All network programs (they reset the Ethernet board)
%    NCSA Telnet (it is a network program)
%    User FTP (it, too, is a network program)
%    format, the DOS format utility for floppy disks
%    FileCommand II

NOTE: Watch memory usage to prevent crashing. Also, remember to
exit when you have finished your DOS activities.



PARAMETER MENU


Press ALT-P to display the Parameter menu options, which appear
on the screen as shown in Figure 3.1. These options control the
settings for text color, echo mode, backspace key, session name,
terminal type, capture file name, screen mode and file transfer
mode. You can change the fields that are shown in bold to
different values.

ALT-P                         Parameter menu
   <      Select parameters, F1 to accept, F10 to leave unchanged      >

   --------------- Color setup and session parameters -----------------
 Text:         normal    reverse   underline
    Normal Foreground (nfcolor)        -    green
    Normal Background (nbcolor)        -    black
    Reverse Foreground (rfcolor)        -    black
    Reverse Background (rbcolor)        -    white
    Underline Foreground (ufcolor)        -    blue
    Underline Background (ubcolor)        -    black
    Use remote echo or local echo        -    Remote echo
    Backspace key sends            -    Delete
    Session name                *>    ahostname
    Terminal type                -    VT102 and Tek4014
   -------------- Parameters which apply to all sessions --------------
    Capture file name            *>    capfile
    Screen mode (for BIOS compatibility)    -    Direct to screen
    File transfer is            -    Enabled


Use arrow keys to select, Enter clears changeable field (*>)

Figure 3.1.  Parameter Menu


The up arrow, down arrow, HOME, and END keys allow you to move the
cursor from option to option. The left and right arrow keys rotate
through the allowed settings for each option. For each field that
you wish to change, move the cursor to that field and press the
left or right arrow until the desired value appears. After
changing all of the fields that you wish to change, press the F1
key to return to your session with the changes in effect. If you
make a mistake, or decide that no changes are necessary, press
F10 to return to your session without any changes taking place.

There are two special fields, marked with the symbol *>, to
indicate that the present value may be changed by typing another.
To change one of these, place the cursor on top of the changeable
field and then press RETURN. The program blanks the field and
allows you to enter a new value. Press RETURN when you are
finished entering the new value. After you enter a new value, but
before you press F1, the old value still remains in memory and
you may use the left or right arrow keys to regain the old value.

Following are descriptions of the parameters you can set.


Screen Text Colors

Host programs expect to be able to control the attributes of
characters on the VT102 screen. Command codes are sent to your PC
to display characters in normal, reverse, underlined, blinking,
and bold attributes, or combinations of these. When normal,
reverse, and underline text are required, you have control over
which colors are used. When blink or bold attributes are required,
NCSA Telnet adds them to your selected colors.

For normal, reverse, and underlined characters, NCSA Telnet gives
you your choice of foreground and background colors, a total of
six settings. The color choices for a PC color video display are
black, blue, green, cyan, red, magenta, yellow, and white. For
each of the text modes, normal, reverse, and underlined, use the
Parameter menu to select the foreground and background colors. As
you change the selections, the sample text on the fifth line of
the screen provides an example of how the text will appear in the
VT102 emulation.

On monochrome screens, when you display a character in the color
blue, the PC produces a visible underline on the screen instead of
blue coloring. Color screens do not have the visible underline
capability and use a visible blue color instead of underlining.
Bold and blinking attributes from the VT102 screen appear as bold
and blinking characters on the PC screen.


Remote Echo and Local Echo

When the response time of the network is long (such as with
satellite transmission), you may want to buffer your keyboard
input locally, only sending characters to the host when you press
RETURN. This is often referred to as a line mode or local echo
mode. The alternative to line mode is called character mode or
remote echo mode, where the local program immediately sends, and
remote host echoes, every character over the network.

In local echo mode, most characters typed at the keyboard are
buffered by NCSA Telnet until you press RETURN, which sends the
characters to the host all in one packet. There are some
exceptions to this rule.

%    CTRL-U erases the local buffer.
%    Backspace (CTRL-H) erases the most recent character added to
the local buffer.
%    Tab (CTRL-I) forces NCSA Telnet to send the local buffer (with
the tab).
%    All other control characters echo with a caret (e.g. ^A) and
force NCSA Telnet to send the local buffer with the control
character included.
%    Arrow keys and all other unprintable ASCII characters, the
escape character for example, force NCSA Telnet to send the
local buffer, with the character included.
%    You cannot send a CTRL-U or Backspace to the host in line mode.
%    ALT keys and other local command keys are not affected by local
echo mode.

NOTE: For full screen editing, character mode (remote echo) is
necessary, so most hosts use this mode. When full screen editing
is not required, line mode may be more efficient.


Function of the Backspace Key

NCSA Telnet automatically translates BACKSPACE keypresses into
DELETE codes, for compatibility with systems that prefer the use
of DELETE to BACKSPACE. If you find that your backspaces are not
being accepted, the host you are connected to may prefer the
reverse setting. To test this possibility, use the Parameter menu
to change the default translation so the BACKSPACE key functions
as backspace. If the result is that your backspaces are accepted,
then the host does prefer the BACKSPACE to DELETE. If you require
the reverse setting frequently, you or your system administrator
may want to permanently reset the backspace function using the
configuration file, as described in Chapter 6.


Changing the Session Name

The status line shows a 14-character session name for each active
session. For each session, the machine name that you typed to
initiate the session displays as the default. The Parameter menu
allows you to change the status line name for the current session.
Press RETURN to clear the current entry and type in a new name.
Only the first 14 characters are used.


Changing the Terminal Type

Generally, the default terminal type of VT102 with Tektronix 4014
is acceptable. There may be specific cases where you need to force
some restrictions on the way the terminal acts, so you may want to
limit the amount of emulation that NCSA Telnet does. The three
choices of terminal types are:

%    VT102 terminal with Tektronix 4014 graphics
%    VT102 only, graphics commands ignored, but VT102 commands
accepted
%    Dumb terminal, no VT100 codes or Tektronix codes interpreted


Changing the Capture Filename

The name of the current capture file can be changed on the
Parameter menu. Press RETURN to clear the current entry and then
enter your new filename. After the name of the capture file has
been changed, all subsequent ALT-C commands use the new capture
file. You can also change the name of the capture file
"permanently" in the configuration file (see Chapter 6). See
Chapter 2 for a description of capture file operations.


File Transfer Mode

The Parameter menu allows you to disable or enable file transfers.
When you select Disabled, neither FTP nor rcp is allowed. When you
select Enabled, the FTP and rcp servers are restarted. Chapter 4
contains more information on the file transfer methods for NCSA
Telnet. The default file transfer modes for FTP and rcp can be set
in the configuration file (see Chapter 6).


Screen Mode (BIOS Compatibility for Windowing
Packages)

In the normal, fast mode, writes are made directly to the screen
for increased speed, but this mode is incompatible with windowing
packages like Topview or Microsoft Windows and may cause snow on
some screens. NCSA Telnet has a compatibility mode where IBM's
BIOS calls are used for all access to the screen.

Usually, the windowing compatibility mode is set up in the
configuration file with the bios option. However, if a change is
needed once you are in the program, the Parameter menu option is
available.








CHAPTER 4

FILE TRANSFER



CHAPTER OVERVIEW


This chapter describes procedures for transferring files between a
PC and a network host, using NCSA Telnet's two built-in file
transfer servers: FTP and rcp. Guidelines and information are
presented for file name conventions, path specification, and
background file transfer.



TERMINOLOGY


The following terms are used in this chapter.

ASCII file, text file

An ASCII or text file can be read by humans, and can be used with standard
editors on the PC or host. When text files are transferred, the end-of-line
markers are changed.

Binary, graphics, or IMAGE file

A binary, graphics, or IMAGE file cannot be read by humans. When
transferred, binary files are not changed in any way (unlike text files).

Client/Server

The client is the system that requests services and the server is the system
that provides them. The client is not always your PC, despite appearances.
When you use NCSA Telnet to connect to a host, your PC is the telnet client.
When you request a file transfer from your PC, the transfer is actually
initiated on the host, making the host the FTP client and your PC the FTP
server. So the PC is a telnet client and an FTP server at the same time.

File transfer

In a file transfer, the contents of a file are copied, and the copy is
placed on another computer's disk drive.



FILE TRANSFER GUIDELINES


Full Path Specification, Conversion of Forward Slashes

With either FTP or rcp, if you do not specify a full pathname,
files are transferred to the default directory. If you need to
specify a different directory, type the full pathname as
documented in the DOS manual. The full pathname may include the
disk drive name, with a colon, for example:

D:\myfiles\graphics\image.dat
or
D:/myfiles/graphics/image.dat

You may use forward slashes (/) rather than backslashes (\),
because NCSA Telnet automatically converts any forward slashes in
UNIX pathnames to backslashes for compatibility with PC-DOS.
Because backslashes are special characters in the UNIX shell and a
special format is required to enter them, forward slashes are more
convenient to use.


Some Simultaneous Activity Permitted

With both FTP and rcp, file transfers are processed at the same
time as other telnet sessions. Therefore, while a file transfer is
in progress you can perform other NCSA Telnet activities such as
interacting with a telnet session, switching sessions, adding new
sessions, or changing parameters.

However, do not initiate another file transfer while one is
already in progress. While an FTP request is being processed, a
second FTP request will be ignored. However, if you try to start
an rcp transfer while another transfer is already underway, both
transfers may fail.

NOTE: Do not quit NCSA Telnet while a file transfer is in
progress, or the file transfer may fail.


Rules for Filenames Sent to the PC

Whether you are using FTP or rcp to transfer files to or from a
PC, check these rules for PC filenames:

%    A legal PC filename is eight characters or less, followed by an
optional period and an up to three-character extension.

%    Upper- and lowercase are considered identical for filenames on
PC disks.

%    Names of files which are transferred from the PC are given in
all lower case.

%    A filename longer than eight characters is truncated.

%    If a period occurs in a filename, the next three characters are
read as the extension, and any others are truncated.

%    A filename should not contain "special characters" or spaces.
If it does, the file may be lost or unreadable. Examples of
special characters are the asterisk (*), the dollar sign ($),
the pound sign (#), the hyphen (-), and control characters.


File Transfer Reports

The FTP server produces several kinds of information for the local
user to help keep tabs on FTP access to the local hard disk.  This
information can be viewed with the ALT-M command (show console
messages), as documented in Chapter 2.  The following list
describes the information which FTP provides:

%    Reports when a command connection is initiated, with the IP
address or host name of the remote machine which initiated the
connection
%     Reports the name of the user who logs in, if the USER
command is used
%     Reports the file names which were transferred to or from
local disk
%     Reports when the command connection ends

The rcp server also produces reports for the console screen.

%    Reports when an rcp transfer begins
%    Reports when the rcp transfer ends



FILE TRANSFER USING FTP


The FTP server in NCSA Telnet is the minimum standard FTP server,
similar to that in 4.2 BSD UNIX. NCSA's FTP supports the following
features:

%    Stream transfer in text format (ASCII) or binary format (IMAGE)
%    Change directory
%    Print current directory
%    List files in current directory (with wildcard specifications)
%    Send and receive multiple files with one command, using
wildcards


Prerequisites

%    The host machine must support FTP file transfer. If you do not
know whether it does, see your system administrator.

%    You must not have disabled the file transfer capability of NCSA
Telnet. That is done with the Parameter menu (Chapter 3), or in
the configuration file (Chapter 6). If the file transfer
capability has been switched off, when you attempt to start up
FTP, you will get a message from the host to the effect that
the computer is not responding. If you get such a message,
check the file transfer mode on the Parameter menu to make sure
that it is enabled.


When to Use FTP

Use FTP rather than rcp in either of the following situations.

1.    You are not thoroughly familiar with the host operating
system. FTP is easier to use than rcp, and requires less
familiarity with the host commands and directory structure.

2.    You are transferring PC text (ASCII) files to a host. FTP is
a better choice than rcp, because FTP automatically converts
the end-of-line characters in text files from CRLF used by PC-
DOS, to LF used by UNIX machines.


Invoking FTP on the Host Computer

FTP is initiated by the host, so the FTP commands vary, depending
on the host system. For full documentation of FTP and commands
within FTP, you must refer to the manuals for the host computer.
With UNIX systems, you can see online documentation by using the
man ftp command.

THE FTP COMMAND

On most systems, the FTP command is entered at the prompt, with
the name or IP address of the target machine. For example, if your
PC is named "mymachine" and your IP address is 192.17.20.22, then
you might enter:

% ftp mymachine
or
% ftp 192.17.20.22

which generates a response like this:

Connected to 192.17.20.22.
220 PC Resident FTP server, ready
Name (192.17.20.22:timk):

Most FTP clients will now prompt you for your username and
password.  If NCSA Telnet is configured for passwords (see Chapter
6), then these are required.  Otherwise, just press RETURN to
bypass the prompts.  If you are  not prompted for username and
password, then assume that you are logged in and continue with
your FTP commands.


ALTERNATE METHODS OF INVOKING FTP (ALT-T AND ALT-I)

The most common procedure for starting FTP uses the shortcut
keystroke, ALT-T. When you press ALT-T, NCSA Telnet types the
ftp command described above, automatically including your PC's IP
address and the RETURN to initiate the command.  For convenience,
you will probably prefer ALT-T to the other ways of entering the
command. You may want to think of this as a keyboard macro that is
pre-set with the FTP command and your IP address.

Another available macro is ALT-I which types your IP address for
you.  When entering any networking command, FTP for example, you
can instantly produce your own network IP address with ALT-I.
The following sequence is equivalent to pressing ALT-T.

ftp
(SPACEBAR)
(ALT-I)
(RETURN)

Use whichever method of invoking FTP you feel comfortable with.
Your host computer may or may not accept FTP commands as described
here, so you may have to try some variations to find the easiest
method for your site.  Your system administrator may be able to
help.


FTP Commands

For most FTPs, after FTP has been invoked and passwords have been
checked, you are prompted for individual FTP commands.  These
commands are also documented in the manuals for the host computer.
Most of the FTP implementations have similar commands because they
are modeled after the Berkeley UNIX version of FTP. Table 4.1
lists FTP commands that are common to most implementations.

Table 4.1.  Common FTP Commands

Command        Action

ascii        Sets mode to ASCII transfer mode (default)

binary        Sets mode to binary (image) transfer mode

cd path        Sets a new default directory on PC

dir        Shows filenames in PC's default directory

get filename    Gets a file from PC, sends to host

help        Shows online list of FTP commands

put filename    Sends a file from host to PC

pwd        Shows current PC directory name

quit        Exits FTP


ASCII, BINARY

The default mode for FTP transfers is ASCII format. If you are
transferring graphics or binary data files, change to binary mode
before you use the put or get commands. Do this by entering the
command binary. To reset the ASCII format after sending a binary
file, enter the command ascii. Figure 4.1 shows an FTP
transaction with an ASCII file. Figure 4.2 shows an FTP
transaction with a binary file.


DEFAULT DIRECTORY

Unless you include a full pathname with the command, NCSA Telnet
transfers the file to the default directory. As Table 4.1
indicates, you can use FTP commands to identify the current
directory (pwd), or change the current directory (cd).

The change directory command, which the user types as cd, allows
you to change the default disk drive in addition to the default
directory.  Just use PC standard disk notation, with forward
slashes instead of backslashes, for example:

ftp> cd D:/files

The pwd command also returns disk information.  After the previous
example cd command, a pwd command returns:

D:\FILES

TRANSFER TO THE PC

Even though you seem to be initiating the transfer from the PC,
the transaction operates from the host's side. The practical
effect of this could make the commands seem
intuitively "backwards." To transfer a file from the host to your
PC, you use a put command. The form this command takes is:

put filename.ext

Figure 4.1 shows an example of a put command used with an actual
file, named temp2. The boldface type represents user entries.


newton_45% ftp -n 192.17.20.124
Connected to 192.17.20.124.
220 PC Resident FTP server, ready
ftp> put temp2
200 This space intentionally left blank <  >
150 Opening connection
226 Transfer complete
262145 bytes sent in 32.61 seconds (7.8 Kbytes/s)
ftp> quit
221 Goodbye
newton_46%

Figure 4.1.  Put to the PC, ASCII File


TRANSFER TO THE HOST

A request to send a file from the PC to the host is called a get.

get filename.ext

Figure 4.2 shows a get operation, using a binary file named
bridge.pic. Note that the file was in the directory named ibmg, so
the cd command was used. Again, the boldface type represents user
entries. If a text file were to be sent after this, the ASCII mode
would have to be reset, using the FTP ascii command.

newton_41% ftp -n 192.17.20.124
Connected to 192.17.20.124.
220 PC Resident FTP server, ready
ftp> bin
200 Type set to I, binary transfer mode
ftp> cd /ibmg
250 Chdir okay
ftp> get bridge.pic
200 This space intentionally left blank <  >
150 Opening connection
226 Transfer complete
262144 bytes received in 9.22 seconds (28 Kbytes/s)
ftp>
ftp> quit
221 Goodbye
newton_42%

Figure 4.2.  Get from the PC, Binary File


FTP STATUS INDICATOR

After you have entered a put or get command, in the lower right
hand corner of your screen you will see the filename and an
indication of the number of bytes transferred (in the case of a
put) or left to be transferred (in the case of a get). These
numbers are updated every couple of seconds to help you keep track
of the progress of the file transfer.  After the command has
completed, the filename goes away and the host usually prints a
confirmation message, as seen in Figures 4.1 and 4.2.


MPUT, MGET

On many telnet hosts, you can transfer multiple files sequentially
with one command, either mput or mget, used with wildcard
characters. (PC wildcard characters are ? for a single character
and * for multiple characters.)


BUG WITH MGET

If you transfer multiple binary files using a UNIX host, note that
there is a bug in mget as implemented on some systems (especially
4.2 BSD UNIX). When used in binary mode, mget adds a carriage
return to the filenames as they are transferred. The files
themselves are not affected. Use a UNIX utility to remove the
carriage return from the filename. In ASCII mode, there is no
problem.



FILE TRANSFER USING RCP


rcp is a Berkeley UNIX feature found in Sun UNIX and other 4.2 BSD
systems. The rcp program cannot do the end of line translation
required for text files, so it is typically used for binary files
only. UNIX rcp is designed for files copied UNIX-to-UNIX, but NCSA
Telnet's rcp server supports transfer between a UNIX system and a
PC.

NOTE: NCSA Telnet's rcp server does not support the recursive
option (-r).


Prerequisites

To use rcp efficiently, you should be familiar with the UNIX host,
including:

%    rcp command and options
%    directory structures used with rcp
%    the relationship between the UNIX shell and rcp wildcards

Details on these concepts are in the manuals for UNIX.

The internet (IP) number and machine name for each PC must be in
the UNIX /etc/hosts file for every machine that is transferring
files to and from your PC.  If rcp does not recognize your PC's
name, have your system administrator check for that name in the
UNIX machine's hosts file.


When to Use Rcp; Advantages of Rcp

Use rcp for binary transfers to or from a UNIX system if you are
familiar with the UNIX hosts, as described earlier.

There are two advantages of using rcp rather than FTP, on binary
file transfers to or from a UNIX machine.

%    rcp handles wildcards more efficiently than FTP does.
%    rcp handles directories more easily than FTP does.


When Not to Use NCSA Telnet's Rcp Server

Do not use the rcp server to transfer text files. Text files on
the PC contain extra RETURN characters that NCSA Telnet's rcp
server does not remove when transferring to UNIX.

NOTE: Do not initiate an rcp while a file transfer is already in
process, or both transfers may fail.


Rcp Between the PC and UNIX

The rcp program is fully documented in the manuals for UNIX hosts
that support rcp transfers.  Refer to those manuals to learn about
rcp.  As a reminder, the general syntax of the rcp command is
given here.  The target filename can be a directory name and
wildcards are allowed, as noted in the next section.

% rcp mypc:filename unixfile        From PC to UNIX.
% rcp unixfile mypc:filename        From UNIX to PC.


EXAMPLE: PC TO UNIX

Following is a sample command to transfer a file named image from
the PC named mypc to the current directory on the UNIX host
(indicated by a dot or period). Note that the only blank spaces
are after the command rcp, and between the filename and the target
directory name (in this case, the dot for the current directory).

% rcp mypc:image .


EXAMPLE: UNIX TO PC

Following is a sample command to transfer a file named mygraf in
the directory graphs from the UNIX host and put it in the
directory grafs on the PC.

% rcp /graphs/mygraf mypc:/grafs


Using Wildcards

Wildcard characters can be used with the rcp command to transfer
multiple files between a PC client and a UNIX host. Wildcards that
refer to UNIX files should be in the UNIX regular expression
format. Wildcards that refer to PC files must be set apart using
backslashes or quotes. See the following examples.


EXAMPLE: BACKSLASHES USED WITH WILDCARDS

One way of using PC wildcards with the rcp server is to use the
backslash character (\) to keep the UNIX shell from interpreting
the special characters. Suppose you want to transfer all files
that have image at the beginning of the filename. Instead of the
usual PC format, image*.*, you must precede each asterisk with a
backslash. The full rcp command would look like this:

% rcp mypc:image\*.\* .

Without the backslashes, the UNIX shell would try to translate the
asterisk on the host rather than on the PC.

EXAMPLE: QUOTES USED WITH WILDCARDS

The second way of using PC wildcards with the rcp server is to
insert quotes around the entire argument. The command to transfer
the files beginning with image would look like this:

% rcp "mypc:image*.*" .







CHAPTER 5

TEKTRONIX 4014 GRAPHICS



CHAPTER OVERVIEW


NCSA Telnet can emulate the Tektronix 4014 graphics terminal. This
emulation includes text modes, Tek 4014 text sizing, zoom, pan,
and multiple output devices. It supports CGA, EGA, Hercules, and
the Number Nine Revolution 512x8 video systems, with the
capability to write out images in PostScript, HPGL, or Tek drawing
commands. The use of Tektronix graphics with NCSA Telnet depends
upon host programs that can produce graphic images. When these
programs run and produce Tektronix 4014 graphics commands, NCSA
Telnet automatically switches into graphics mode and does the
drawing.

This chapter describes steps in preparing to emulate the Tektronix
4014 and how to use the Graphics menu.



BEFORE YOU BEGIN TEKTRONIX EMULATION


Initializing a Plotter

If you will be plotting directly to a plotter, the communications
port for the plotter must be initialized before you run NCSA
Telnet. This is done using the DOS mode command. See the DOS
manual and the plotter manual for examples.


Configuration File Settings

The configuration file is used to install the hardware and
software configuration for Tektronix graphics. There are several
settings you should insert in the configuration file, detailed in
Chapter 6, before you use Tektronix emulation.

1.    You should include tek=yes in the configuration file to
enable graphics operation.

2.    The video type is specified with the video parameter in the
configuration file. This is the only step required for
selecting the video display because all of the screen drivers
are included in NCSA Telnet.

3.    You should install specific filenames to be used when
writing each of the three different kinds of drawing commands.
The hpfile parameter selects the file to receive HPGL commands,
the psfile option selects the file to receive PostScript
drawing commands, and the tekfile option selects the file to
receive Tektronix drawing commands. If you do not make any
settings here, the default files are hp.out, ps.out, and
tek.out.

4.    If you want HPGL output to go directly to a plotter that is
connected to COM1 rather than to a disk file, add hpfile=com1
to your configuration file. Note that COM1 is used without a
colon.



SWITCHING TO AND FROM GRAPHICS MODE


Graphics Mode

When host programs produce Tektronix 4014 graphics commands,  NCSA
Telnet automatically switches into graphics mode and does the
drawing.  The exact command sequence which causes the switch to
graphics mode is the Tektronix clear screen command, ESC-FF, which
is sometimes written as ESC-CTRL-L. A copy of your text screen is
saved while you are in graphics mode.

The second way to enter graphics mode is to press CTRL-HOME.
This key switches from text mode to graphics mode and clears the
graphics screen. Host programs that produce Tektronix 4014
graphics commands cause the screen to automatically go to graphics
mode, so you will not usually need to use CTRL-HOME to switch to
graphics manually.

The third method of starting graphics mode is to re-display the
last graphics image. The re-display option is from the Graphics
menu, described later in this chapter. At the completion of the
re-display command, the screen remains in graphics mode.


Text Mode

To return to text mode, press HOME. When you are in graphics
mode, HOME will set your display back to text mode and redraw the
text screen which was visible before the graphics mode began.
There is no host command which automatically returns to text mode.
When you are in text mode, HOME has a different function. See
Chapter 2 for details.


GRAPHICS MENU (ALT-G)


The Graphics menu is started with ALT-G. Figure 5.1 shows the
Graphics menu, as it appears with the default file names. The
fields in bold can be changed by the user.


ALT-G                           Graphics menu
<            Press the appropriate function key or ESC to resume        >

   F1 - Write postscript to a file called: ps.out
   F2 - Change postscript output file name

   F3 - Write HPGL code to a file called: hp.out
   F4 - Change HPGL output file name

   F5 - Write Tektronix 4014 codes to a file called: tek.out
   F6 - Change Tektronix output file name

        View region is currently: 0,0,4095,3119
   F7 - Set a new view region (Zoom, Pan)
   RETURN - draw picture on screen in current zoom factor

   Enter choice:

Figure 5.1. Graphics Menu

From this menu, you press the appropriate function key, or RETURN
to redraw the most recently displayed graphics picture.


Writing Graphics Files to Disk

To write out graphics images use the Graphics menu. First, the
image should be displayed on the screen using host software that
generates Tektronix images. NCSA Telnet always keeps the last
graphic image in memory. Select one of the options which writes
this image to disk. Images are written using the current view
region.

If you select Tektronix 4014 format, NCSA Telnet writes the image
directly to disk and then returns you to your current session.
After selecting the HPGL or the PostScript option from the
Graphics menu, you are returned to your session while the file is
written to disk in the background. After this image has been
completely copied from memory to disk, you are notified on the
console screen that the process has completed.


Renaming Graphics Output Files

If you did not set up alternate files to use in the configuration
file and you do not want to use the default filenames hp.out,
ps.out, or tek.out, you can change the names before or after
writing the file. Use the Graphics menu options to change one of
the current file names before writing the image to disk. If you
want a name change after writing out the file, use ALT-E to escape
to DOS, then use the DOS rename command. Use exit to leave DOS and
return to NCSA Telnet.

A special feature allows you to append the current image to an
existing disk file instead of overwriting.  Enter any of the three
file names as you would normally, adding a plus (+) to the
beginning of the name.  NCSA Telnet takes the plus (+) to indicate
that you want to open that file for "append", adding another image
to the file.  A filename which does not begin with a plus (+),
causes NCSA Telnet to overwrite the file when saving each image.


Set the Viewing Region (Zoom Factor)

Another Graphics menu choice lets you set the viewing region, or
zoom factor. Any portion of the image can be enlarged and made to
fill the screen. Tektronix drawing commands are resolved to a 4096
by 3120 pixel resolution. They start with 0,0 in the lower left,
and go to 4095, 3119 in the upper right.

The default view region for NCSA Telnet is (0, 0, 4095, 3119),
which is the full image. Figure 5.1 has examples of possible
viewing regions that you can use.



Figure 5.2. Sample Viewing Regions

Redraw Last Image

The Graphics menu option, Redraw Last Image, is used when you want
to review the image that is currently in memory. This option
always zooms and enlarges the image according to the view region
that is visible. The selected view region always fills the screen
so you can see more detail.

This command leaves you in graphics mode, so press HOME if you
want to return to text mode.



PLOTTING A STORED FILE


If you have used the Graphics menu to store a file of HPGL drawing
commands, the DOS copy command can send those commands to an
attached plotter (which is connected to COM1 in this example).

C:> copy filename.out com1









CHAPTER 6

INSTALLATION AND CONFIGURATION



CHAPTER OVERVIEW


This chapter contains information for system administrators (and
other experienced users) to use in installing and customizing a
system. The chapter describes how to install NCSA Telnet, change
the configuration file, the domain name lookup, how to protect FTP
transfers with passwords, and compatibility issues.



INSTALLING THE DISTRIBUTION FILES


There are three files required for the standard configuration of
NCSA Telnet. The combination of these with the use of the DOS path
command allows you to call up NCSA Telnet from any subdirectory on
your PC.

TELNET.BAT

This batch file begins the execution of NCSA Telnet. It must be in some
directory that is in your DOS path. It contains the locations of the
TELBIN.EXE and CONFIG.TEL files. You must update this batch file (with any
standard editor) when you change the location of TELBIN.EXE or CONFIG.TEL.

TELBIN.EXE

This is the program itself. It can be in any directory. The TELNET.BAT file
calls up this program when it runs.

CONFIG.TEL

This is the configuration file that contains your PC's IP address, the kind
of Ethernet hardware that you are using, and other information about your
network. Gateways, nameservers, and setup information are stored here. The
TELNET.BAT file tells TELBIN.EXE where it can find this file on your disk.


Sample Configuration

Suppose you want to install NCSA Telnet in a directory called
\ncsa on your hard disk drive, drive C. Copy the TELBIN.EXE and
CONFIG.TEL files to C:\ncsa. Suppose also that you have a
particular directory C:\bat, which you use to store commonly used
batch files. Your DOS path (see DOS manual) contains an entry for
C:\bat already. Copy the TELNET.BAT file into C:\bat. You must now
edit the TELNET.BAT file to update the locations of the TELBIN.EXE
and CONFIG.TEL files. When finished, it should look something like
this:

if .%1 == . goto defh
c:\ncsa\telbin -h c:\ncsa\config.tel %1 %2 %3 %4 %5
goto exith
:defh
c:\ncsa\telbin -h c:\ncsa\config.tel ncsab
:exith

This batch file calls up TELBIN.EXE at a known location and passes
it the -h parameter, indicating the location of the CONFIG.TEL
file. In addition to the file locations, the fifth line indicates
which machine NCSA Telnet should connect to by default.


Required Configuration Information

To set up a new configuration file, you will need a standard text
editor. The template provided with NCSA Telnet is set up to
reflect commonly used default values. It may be worth the time to
go through the list of configuration options in this chapter and
fine-tune your configuration to match your local computing
situation more closely. In the meantime, the following fields in
the configuration file must be installed for NCSA Telnet to
operate.


myip=192.17.20.10

You must provide a unique IP address for
each machine on your network. This must be
installed in the configuration file of
each computer.

netmask=255.255.255.0

Subnet mask, in decimal. This field is
required if you are using subnets on your
network.

hardware=3C501

NCSA Telnet can support several different
brands of Ethernet adapters. Each brand
has its own unique identifier which must
be set for the hardware parameter. See the
hardware section in this chapter for a
complete list of settings. Most brands
also require address and ioaddr to be set.

video=ega

If you wish to use the Tektronix graphics
options, you must provide the correct
screen type. Incorrectly installed, this
can crash NCSA Telnet. The alternative is
to install the tek=no option. Legal types
are cga, ega, hercules, no9.

gateway=1

If you are going to be using gateways to
reach other networks, at least one machine
must be designated as a gateway, using
this gateway option after the name field.
The entry for each gateway must include a
hostip field, according to the
configuration file directions in this
chapter.


The TELNET.BAT File

The actual .exe file that the PC executes is not named telnet.exe.
A batch file called TELNET.BAT loads the software in several steps
that are normally transparent to you. Here is a typical entry in
TELNET.BAT:

C:>\apps\telbin -h c:\apps\config.tel %1 %2 %3 %4

The TELNET.BAT file, which must be in the DOS path, specifies
completely where the program is, and where the configuration file
is to be found. There may also be a default machine name that the
system connects to when you do not explicitly specify one.


Command Line Options

Telnet goes through two stages as you load it. The TELNET.BAT file
must be in the DOS path so it can be found first. In the batch
file, the location of the TELBIN.EXE file and any command line
defaults are used to call up the program in the next stage. Many
command line arguments are included for you in the batch file,
TELNET.BAT; you add others when you run the telnet batch file.
This is a full description of those options. The syntax for
loading NCSA Telnet with options is:

C:\ > telnet [options] [machine1 machine2 ...]

The options must precede the list of machine names on the command
line. Options can be in any order; parameters on options are
required. There must be one space between the options and between
each option and the parameter for that option. The options are:


?

Shows command line options. This causes NCSA
Telnet to display a summary version of the
command line options instead of initiating the
program.

-c colorcode

Sets the default color for screens. The
colorcode string is six digits long and follows
the coding scheme documented later in this
chapter.

-h filename

Specifies where to find the configuration file.
Normally, this option is included in TELNET.BAT,
and you never have to use it explicitly. If the
configuration file is not specified there or on
the command line, there must be a file named
CONFIG.TEL in the default directory. If a
suitable configuration file cannot be found
according to these rules, NCSA Telnet
terminates. NOTE: filename should include a
pathname. For example,

            C:\bat\config.tel

-s

Enters server mode. NCSA Telnet waits for
external FTP and rcp requests. It allows you to
leave your PC and access files there from a
remote machine.

-t

Disables direct writes to the screen. Without
the -t option, NCSA Telnet defaults to writing
directly to screen memory. This greatly enhances
the screen speed, but makes NCSA Telnet
incompatible with Topview, Microsoft Windows,
and other windowing systems. To make NCSA Telnet
completely compatible with BIOS-level programs,
use the -t option. This option can be
permanently installed in the TELNET.BAT file or
the CONFIG.TEL file (bios option).



THE CONFIGURATION FILE


Overview of the Configuration File

The configuration file replaces the hosts file of NCSA Telnet
Version 1.2. This file contains information on local operating
parameters (such as which type of graphics screen your PC has, and
your IP number), plus a list of commonly accessed hosts and
optional network tuning parameters for each of those hosts.

The configuration file is accessed once when the program is
initiated and is not used again. All of the machine names are read
into memory, so it may save memory to limit the number of
computers you specify in the file.

The configuration file is typically named CONFIG.TEL. If this file
is in the default directory, it will be found automatically, but
the use of the -h flag in the TELNET.BAT file is recommended.


Syntax for Entries in the Configuration File

The configuration file is a list of keywords and values for those
keywords. The one overall requirement for the entries in the file
is that they alternate, keyword then value, keyword then value,
and so on. There are many different formats possible using any of
the allowable delimiters. The delimiters are the colon (:),
semicolon (;), equal sign (=), and any of the whitespace
characters. To include delimiters in a value field, enclose the
field in double quotes. Quotes cannot be a part of the actual data
field. Wherever a pound sign (#) is found, everything from there
to the end of line is a comment. Though multiple formats can be
used in the same file, you will probably want to find and keep a
consistent format. For example, each of the entries in Figure 6.1
specify the same information.

Note that example #3 is not a recommended format, but is included
to show how strange an entry may look.

    name=nic      # comment field to end of line ->
    host=sri-nic.arpa
    hostip=10.0.0.51
    scrollback=300
    contime=60

- - - - - -Example #1- - - - - - - - -



    name=nic; host=sri-nic.arpa; hostip="10.0.0.51"; scrollback=300; contime=60

- - - - - -Example #2- - - - - - - - -



    name
    nic
    host sri-nic.arpa : hostip=10.0.0.51; scrollback=300; contime:60

- - - - - - Example #3- - - - - - - - -


Figure 6.1.  Displaying the Same Information in Different Entry Formats



PC Information Entries in the Configuration File

The first entries in the configuration file are the PC environment
entries. They specify what types of hardware are to be used, names
of graphics output files, and network configuration information.
Here is the list:


myip=10.0.0.51

This is the IP address to use for the PC.
This number must contain all four parts of
the IP address. This field is required.

myip=RARP

This is a special form of the myip entry.
Setting myip to RARP will cause NCSA
Telnet to query a RARP server to get its
IP address. See the section on RARP in
this chapter.

netmask=255.255.255.0

This is the subnet mask for your local
network. It is optional for networks
without subnets.

arptime=3

Specify how long to try to reach a host on
the local wire, in seconds. A value of 2
works fine for the network at NCSA, but
larger values may be needed for hosts that
are slow to respond. Smaller values are
more convenient to use.

domain="ncsa.uiuc.edu"

This entry in the configuration file
affects hostname lookups which are sent to
the domain nameserver. All names which do
not contain a period have the default
domain appended before the nameserver
request goes out. If the hostname you type
contains a period, then the name is
unmodified before NCSA Telnet sends it to
the nameserver. There is no "ring-down" or
multiple lookup feature to try more than
one form of the name.

domaintime=2

Time in seconds to wait between the first
domain lookup and the second. If you only
have one nameserver, then this is the same
as a simple timeout. If you want to rotate
nameservers quickly because the first one
may be down, set this to a smaller number.
To force a larger number of retries, set
this to a smaller number. To wait longer
for a domain response, increase this
value.

domainretry=4

Number of times to query domain
nameserver(s). Each time a retry is sent,
the timeout value (above) is doubled. Each
time a retry occurs, NCSA Telnet tries the
next nameserver, wrapping around to the
first nameserver when there are no more.

tek=yes

There is no overhead to unused Tektronix
graphics emulation, but you may wish to
disable graphics support. tek=no will
disable Tektronix graphics emulation.

video=ega

Tektronix 4014 graphics emulation is
included in NCSA Telnet for a variety of
video devices. Supported are: hercules
(Hercules monochrome graphics), cga (IBM
and compatibles original Color Graphics
Adapter), ega (IBM Enhanced Graphics
Adapter and compatibles), and no9 (Number
Nine Computer's Revolution 512 x 8 board).

bios=no

NCSA Telnet has two screen-writing modes.
One is direct-to-screen (bios=no) which is
considerably faster on most machines. The
other uses BIOS (bios=yes) and follows the
IBM BIOS conventions at all times. BIOS
mode makes NCSA Telnet compatible with
popular windowing systems and can reduce
the amount of flicker and snow on the
screens of IBM CGA-equipped systems.

hardware=3C501

NCSA Telnet can support several different
brands of Ethernet adapters. Each brand
has its own unique identifier which must
be set for the hardware parameter. See the
hardware section in this chapter for a
complete list of settings.

interrupt=3

There are several choices for interrupt
vector on the 3COM 3C501 Etherlink board.
NCSA Telnet defaults to IRQ3, but can be
set to use different interrupts by
indicating the interrupt number here.
Match this number with the interrupt
setting from your Etherlink board.

address=d000

This is the segment address of the
Ethernet board's shared memory, entered
as four hex digits. This only applies to
boards that have jumpers or registers
which can be used to set the shared
memory address. After setting the board's
jumpers to a particular value, use the
address parameter to configure NCSA
Telnet with the same setting. d000 (hex)
is a common address to use and it rarely
conflicts with other boards.

ioaddr=360

This is the I/O base address of the
Ethernet board in hex. Some Ethernet
boards have selectable I/O addresses.
These generally range from 200 to 400
(hex) and must be entered as two, three,
or four digits.

ftp=yes

FTP serving is enabled by default. Access
to your PC can be controlled by the FTP
password file. To disable FTP serving
completely, change this line to ftp=no.

rcp=yes

rcp serving is enabled by default. To
disable rcp serving, change this line to
rcp=no.

capfile=

Specify a name for the capture file. For
example,

    capfile ="c:\temp\myfile"

    When you capture to disk, all data is
appended to this file. If no name is
included in the configuration file,
capfile is used by default.

capfile=prn

Specifies that the printer device (PRN)
should be used for the capture file.

hpfile=hp.out

Tektronix graphics can be dumped to a file
in several formats from the Graphics menu.
When you write out HPGL (HP plotter)
codes, this file name is used. For
example,

    hpfile="c:\hpgrafs\hp.out"

    The default is hp.out in the current
directory.

hpfile=COM1

With an HP plotter hooked up to your PC,
HPGL plotter codes can be sent directly to
the plotter. Use the mode command to
preconfigure the serial port first.

psfile=ps.out

PostScript commands can be printed by
several types of available laser printers.
NCSA Telnet's PostScript output has been
tested on the Apple (Sun) LaserWriter,
which is connected to Sun workstations.
The default filename is ps.out in the
current directory.

tekfile=tek.out

Tektronix 4014 graphics commands are a
very compact way to store a Tektronix
graphics image. This option specifies the
filename to use when you write Tektronix
codes to disk. The default name is
tek.out.

passfile=

Specify the file in which FTP usernames
and passwords can be found. For example,

    passfile="c:\bat\ftppass"
    There is no default name for this file. If
the file is specified, then FTP will
require a username and password for all
attempted FTP connections. If the file is
not specified, then there is no password
checking for FTP. Use the program
TELPASS.EXE to encrypt new passwords. See
the FTP Password Protection section later
in this chapter.




Host-Specific Parameters of the Configuration File

Following the PC configuration options, you may specify zero or
more hosts, and host-specific information for each host. By making
the host entries in the configuration file, you can specify color,
backspace, scrollback, connection timeout, and several tuning
parameters for each host. You may want to have more than one
session name associated with a single computer, such as purple
cray and red cray with different screen colors to fit your mood of
the day.

Typically, the first host listed will be name=default, which
stores the default values for the other hosts. Any keyword listed
under later hosts will override the default setting for that host
session.

NOTE: The keyword name is special because it separates entries.

The parameters following name up to the next keyword name are all
associated with the session name. The parameters are installed
whenever a connection is opened with that session name.


name=nic

The name that you want to appear on the
bottom line of the screen when the
connection opens. It is the primary name
associated with a list of parameters. It
is common to have more than one session
name for a host, each with different
parameters, perhaps with different colors
or different amounts of scrollback. This
parameter is required because it separates
entries.

host=sri-nic.arpa

This is the hostname or alternate name. If
you want to associate both a session name
and a hostname with a particular set of
parameters, you may include both. Note
that the name parameter is required, while
the host parameter is optional. The rule
of thumb is: When you have only a
hostname, insert it as name=hostname. If
you have both a session name and a
hostname, enter both name=sessionname  and
host=hostname. When you want to open a new
connection, either hostname or sessionname
works.

hostip=10.0.0.51

This is the IP address of the host. If
this is not present, the domain nameserver
must be queried to get the IP number of
the host. For efficiency, include the IP
addresses of all commonly accessed hosts.
IP addresses of gateways and nameservers
must be in the configuration file.

copyfrom=nic

The copyfrom parameter is probably the
most important one. It causes all
unspecified parameters to be copied from a
previous session name. Note that the
session name which you want to reference
with copyfrom must appear before the
session name that uses a copyfrom
directive. Parameters that are specified
for a session name along with a copyfrom
directive override that copyfrom
directive.

gateway=1

This specifies the gateway precedence for
this host. To reach hosts not connected to
your local network, you must have at least
one gateway entry. The hostip keyword must
be present for this host. Gateway numbers
must start at 1 and increase by ones.
Gateway 1 has the highest precedence, but
the first gateway to respond to an ARP
will be used. ICMP redirects can affect
how gateways are used, but not
permanently.

nameserver=1

This specifies the nameserver precedence
for this host. NCSA Telnet uses UDP to
query domain nameservers for machinenames
that are not in the configuration file.
Each machine that is to be used as a
nameserver must have this keyword listed.
The hostip keyword must be present for
this host. Nameserver 1 has the highest
precedence. Nameserver numbers must start
at 1 and increase by ones.


nfcolor=white        normal, foreground
nbcolor=black        normal, background
rfcolor=black        reverse, foreground
rbcolor=white        reverse, background
ufcolor=blue        underline, foreground
ubcolor=black        underline, background

    These new color options can be used
instead of the more complicated color code
from previous versions. For each value,
specify a string from the following list
of colors available on IBM-PC class
machines with color displays:
    black
    blue (underline on mono screen)
    green
    cyan
    red
    magenta
    yellow
    white

    The foreground and background colors are
combined to create the text appearance on
the screen. You may wish to experiment
with the Parameter menu (Chapter 3), which
interactively allows you to select a color
scheme. The previous version's color=
entries are still supported.

scrollback=100

This specifies the number of lines of
scrollback for this session. Be aware that
scrollback occupies at least 86 bytes per
line saved. There can be a different
number of lines of scrollback for each
session. Plan your use of scrollback
wisely unless you have memory to spare.

clearsave=yes

Scrollback is updated when the screen is
cleared. When clearing the screen, all of
the visible lines are saved into the
scrollback region. If you prefer not to
have the text saved when the screen
clears, set clearsave=no. In the case of
host programs which clear the screen one
line at a time, the lines are never saved
into the scrollback region.

erase=delete

This sets the backspace translation for
this host. Some hosts prefer the backspace
key to be DELETE and some prefer the
backspace key to be BACKSPACE. Set this
value erase=delete or erase=backspace.

crmap=4.3BSDCRNUL

This is a special compatibility option for
4.3 BSD UNIX. There is now a UNIX bug fix
to take care of the problem, but some
hosts may still want crnul to be used for
end-of-line. The default is crmap=crlf,
which sends CRLF when you press RETURN. In
line mode, CRLF is always used.

duplex=half

This parameter only applies to hosts that
negotiate non-echoing mode but do not
expect local line editing. All character
keys are sent and echoed to the screen
immediately. This parameter has no effect
in echo mode.

contime=10

This is the connection timeout in seconds.
When you are making a connection attempt,
after this amount of time has elapsed NCSA
Telnet gives up on opening the connection
and deletes the window. For congested or
slow networks, this value should be made
larger.

retrans=7

This is the initial retransmit timeout in
18ths of a second. Increasing the value of
this parameter may help in reducing the
initial burst of retries that is typical
of connections with high round-trip times.

mtu=512

This is a byte count (1-1024) of the
largest amount of data to put in the
packets that are sent. If you are sending
to the ARPANET you should use mtu=512. If
you are sending to local hosts, you should
use mtu=1024.

maxseg=512

This is a byte count (1-1024) of the
largest TCP segment that can be received.
This value can control the size of packets
that are sent over the connection.
Reducing this value can eliminate IP
fragmentation that we cannot reassemble.
maxseg=512 should force the sending host
to never fragment.

rwin=512

This is a byte count (1-4096) of the
largest size of the TCP window to
advertise to other hosts. Unfortunately,
some hardware and networks, the 3COM 3C501
Etherlink for example, cannot handle
receiving back-to-back packets. This
requires us to limit the TCP receive
window that we advertise to other hosts.
For communicating to slower hosts, or when
using the other brands of Ethernet boards,
a larger window (4096) may work better.


Converting UNIX /etc/hosts Files

Included with the distribution is an awk script called newh. Used
with the following command under 4.X BSD UNIX, it will convert the
/etc/hosts file format into a format compatible with NCSA Telnet's
configuration file. Note that domain name lookup should make this
operation obsolete, or apply to only a small subset of your
/etc/hosts file.

% awk  -f newh /etc/hosts >config.temp

After creating this new file, prepend the PC-specific information
and download the file to the PC.



HARDWARE OPTIONS


Combined Ethernet Drivers

There is only one distribution program for NCSA Telnet Version
2.2. All of the Ethernet and video device drivers are combined
into one executable program. You must use the hardware entry in
the configuration file to inform NCSA Telnet which Ethernet board
you have installed. Choose from the list of supported Ethernet
boards in Table 6.1; the value to use is case insensitive. The
requirements for interrupt, address, and ioaddr entries in the
configuration file are listed.
Table 6.1.  Ethernet Boards Supported by NCSA Telnet

hardware=

Value        Ethernet Board            Requires
For PC bus -
3C501        3COM 3C501 Etherlink        interrupt,ioaddr
PCNIC        Ungermann-Bass PC-NIC         address,ioaddr
        or IBM Baseband adapter
NI5210        MICOM NI5210             address,ioaddr
WD8003        Western Digital WD8003E     address,ioaddr

For PS/2 MCA bus -
NICps2        Ungermann-Bass NICps/2         address
3C523        3COM 3C523 Etherlink/MC     address,ioaddr



Performance Tuning

The values of maxseg, mtu and rwin in the configuration file must
be set correctly to get maximum data transfer throughput between
machines. There are some rules of thumb to use when setting these
values.

%    The maximum reasonable values for these parameters are:
    rwin=4096
    mtu=1024
    maxseg=1024

%    The best setting for local network use, with a high performance
Ethernet board is:
    rwin=4096
    mtu=1024
    maxseg=1024

%    The best setting for ARPANET use, or any situation with a lot
of unknown gateways, but with a high performance Ethernet board is:
    rwin=4096
    mtu=512
    maxseg=512

%    The setting required for the 3COM 3C501, and any other
troublesome network situation, also the most conservative
setting, is:
    rwin=512
    mtu=512
    maxseg=512

rwin specifies what the other computer is allowed to send you at
any one time, so it depends mostly upon your local Ethernet board.
If the board can handle it, always set rwin=4096. maxseg is used
to avoid fragmentation. If you get fragmented packets, lower the
value of maxseg for that host until fragmentation stops occurring.


RARP for Dynamic IP Address Assignment

myip=RARP

When this special form of the myip entry is used, NCSA Telnet
looks up your local machine's IP address with a broadcast request
to the network. The "Reverse Address Resolution Protocol" is used
to attempt to translate the local machine's assigned 48-bit
Ethernet address to a corresponding IP address. From our tests
with the RARP server from Sun Microsystems' SunOS 3.X, the RARP
lookup takes about 3 seconds. You must install the 48-bit Ethernet
address from each PC in the RARP hosts' tables before RARP will
work. The value of arptime, in seconds, multiplied by three, is
used for a timeout value.

NOTE: Sun's RARP lookup will not work if you have a double-zero
in your Ethernet address. Other leading zeros can be dropped as
well. Use a single zero, i.e. 8:0:20:1:5a:90, instead of
08:00:20:01:5a:90.


Interrupts

When you configure the 3COM hardware, an important option is the
choice of interrupt request number (level). 3COM boards arrive set
for IRQ3, which corresponds to the PC-DOS definition of the COM2
communications port. If you have a port configured as COM2, you
cannot set your Ethernet board to IRQ3. Another common value to
use is IRQ5, which is the same interrupt that DOS uses for LPT2.
Make sure that your PC hardware configuration does not conflict in
any way.

WARNING

The most common hardware problem is interrupt conflicts.
PCs have a limited number of interrupts, and you cannot have two
devices which expect to use the same interrupt. PC Ethernet boards
almost always consume an interrupt, even though we do not use
interrupts for all Ethernet boards. Interrupts are also used by
COM ports and LPT ports in your machine. You must check for
conflicts.

Even though it works, it may stop working. Interrupt
conflicts don't always show up right away. They are software
controlled. If the interrupt on your COM2 port is not activated,
it may not conflict with a 3C501 board on IRQ3 until next week
when you try to use a modem terminal emulator and then switch to
NCSA Telnet. NCSA Telnet might work fine until you try to FTP to
your hard disk; then disaster strikes.

Hard disks use interrupts too. We have traced two serious
hard disk problems to interrupt conflicts. IRQ2 is the default
setting for some Ethernet boards when they come out of the box. On
a PC-AT, this interrupt is used for the second interrupt
controller, and a conflict can shut off the whole second
controller which includes the hard disk. On the PC/XT and PC
compatible computers, IRQ5 is sometimes assigned to the hard disk
rather than LPT2. Strange hard disk problems like disk write
errors may be caused by the Ethernet conflicting with the hard
disk.

Moral:  Set your Ethernet board to an unused interrupt.



DOMAIN NAME LOOKUP


When NCSA Telnet cannot find a name in the configuration file, it
can still find the IP number if you are running a domain
nameserver. To use the domain system, at least one host must be
running the nameserver and the configuration file has a nameserver
entry for that host. There may be more than one. If one nameserver
fails to respond, the one with the next higher precedence is
queried. As soon as a response is received, NCSA Telnet will add
its name to the status line and attempt to open a telnet
connection.


Domain Search Order

When you enter a name to open a connection, there is a specific
search order:

1.    The name is looked up as a session name from the
configuration file.

2.    The name is looked up as a hostname from the configuration
file.

3.    The name is sent as a domain query to the first nameserver.

4.    If the domain request times out, the query is repeated, but
to another nameserver. This is repeated until the maximum
number of retries is reached or a response is received.

With the domain nameserver, the number of hosts in the
configuration file can be kept to a minimum. Each host in the
configuration file will be a commonly used computer that may have
special screen color or scrollback requirements. The IP addresses
for rarely used hosts will be accessible if the domain name
retrieval system can resolve those hosts.



FTP PASSWORD PROTECTION


The presence of the passfile keyword in the configuration file
enables FTP password protection. If you have a password file, FTP
will not allow any FTP connections to open without a correct
username and password. You can have several usernames and
individual passwords for each user. The password file can be
easily read by typing out the file. The passwords are encrypted,
but not with a secure encryption system. Only trusted users should
be allowed access to the password file.

To create or change passwords for users, run a separate program
called Telpass. This program reads in the password file so you can
add and change users and passwords. There are no special
installation instructions for Telpass as it is menu-driven. Start
up Telpass from DOS with the name of the password file that you
wish to edit.

C:\ telpass pwfile

Telpass automatically saves the list of names and passwords when
you exit. Just add a passfile option to your configuration file to
enable FTP passwords.



COMPATIBILITY NOTES


Ping

NCSA Telnet responds to ping (ICMP echo) requests. This is used by
other hosts to determine whether your PC is online.


VT102

The VT102 emulator is nearly complete. VT102 features not emulated
are double width and double height characters, VT52 mode, origin
mode for cursor positioning, and 132 column mode. Included in the
emulator are variable spaced tabs, graphics characters, keypad
modes, and character attributes.


FTP

The FTP server in NCSA Telnet is close to the DARPA specification
of the minimum implementation. Exceptions are:

%    The command connection does not perform telnet negotiation.
%    Block mode of FTP is not supported.
%    Some error conditions may display as command not understood
instead of returning more appropriate messages.

FTP has not been thoroughly tested on low-bandwidth or low-
reliability networks. It should be most successful on local
networks, with unknown throughput for long-haul or satellite
networks.


Terminate and Stay Resident (TSR) Programs

Programs such as SideKick from Borland International Inc. take
complete control of the PC when they are initiated with key
sequences. The use of these programs does not crash NCSA Telnet,
but it suspends the network communications capability while the
TSR program is active. When network communications are suspended,
whether from the ALT-E DOS escape feature or from using TSR
programs, it takes the host approximately one minute to decide
that your PC has crashed, and then it cuts you off. As long as
these programs are used for short (less than 30 seconds)
intervals, you should have no problem.


Telnet

The standard telnet protocol has several potential options that
can be invoked if both parties of the telnet connection agree.
NCSA Telnet refuses most of these options, but accepts the
following: echo, option 1; and suppress go ahead, option 3. There
are some obscure features of telnet that are not implemented in
this version: out-of-band interrupts are not available, go ahead
signals do nothing, and telnet acknowledge signals are not
acknowledged. If there are any problems with the limitations of
NCSA Telnet, please submit a bug report.


Limitations

There is a 20-session limit for NCSA Telnet. This is somewhat
arbitrary and may be altered if there appears to be a need for it.
NCSA Telnet can run out of memory, often before the 20-session
limit. You are notified on the screen if this happens.







APPENDIX A

ERROR CONDITIONS



Most of the error conditions in NCSA Telnet are nonfatal. The most
important and common error messages are listed here with a short
summary of the symptoms and causes.

The following messages may appear on your screen during the
operation of NCSA Telnet. Any other messages that appear are
protocol-specific messages that require additional diagnosis from
the system administrator. If a message that is not documented here
occurs repeatedly, please contact your system administrator first,
and if no solution is found, submit a bug report as included in
this manual.


Cannot find or open hosts file

Cause:
NCSA Telnet will not operate without a configuration file that
contains the PC's IP address. This file could not be found.

Solution:
The configuration file can be either in the current directory, or
it can be specified with the -h parameter on the command line.
This is normally customized in TELNET.BAT. Your system
administrator should check your installation and make sure the
configuration file is there.


Host machine not in hosts file

Cause:
You have entered a machine name that cannot be found in the
configuration file. This usually is caused by a misspelling.

Solution:
Check that the name you entered was spelled correctly. If you want
this computer to be accessed by name, add its name and IP address
to your configuration file.


ICMP:    Destination unreachable

Cause:
Another machinePPprobably the gatewayPPhas determined that your
message cannot reach its destination from your system.

Solution:
Check the IP address in your configuration file. Notify your
system administrator that the gateway cannot connect you to the
destination you want to reach. There may be a problem with the
gateway.


ICMP:    Echo requested (ping requested)

Cause:
Someone has "pinged" your machine.

Solution:
No action is required; you are just being notified that a program
on another computer has tried to determine if your machine is
alive and connected to the network. Your machine answered "yes".


ICMP:    Redirect, another gateway is more efficient

Cause:
NCSA Telnet is sending packets to a gateway that is reforwarding
them onto your local network. You will get one of these messages
for each packet until NCSA Telnet adjusts the local tables and
automatically switches to the correct gateway.

Solution:
NCSA Telnet responds to these messages and automatically switches
to the correct gateway, so you don't have to take any action.  You
may want to change the gateway assignments in your configuration
file to use a more appropriate gateway.  Some situations will
always produce redirects.


Local HOST or gateway not responding

Cause:
Possible reasons this error occurs are: network problem, a
configuration file problem, the computer you want to connect to is
down, or the gateway that you need is down.

Solution:
If the computer is on your local network, check to see that the
network is up and running. If the computer is not on your local
network, check to see if the gateway is up and running. Ask the
system administrator to check the specification of the gateway
(gateway=) in your configuration file. Check the IP number of the
computer that you are trying to connect to. Check to make sure
that your computer is attached to the network. Check the integrity
of the network cable.


Memory allocation error, cannot open port

Cause:
Your system ran out of memory. This is the most common barrier to
opening more sessions.

Solution:
Log off of some of your sessions or provide more memory in which
NCSA Telnet can run. Providing more memory may mean buying more or
rearranging your windowing system to allow more memory. NCSA
Telnet Version 2.2 requires about 250K of memory plus 15K per
session. In addition, scrollback requires 86 bytes per line.


Network jammed, probable break in wire

Cause:
The PC's Ethernet board could not transmit a packet due to a low-
level hardware error.

Solution:
The system administrator should ensure that the Ethernet T
connector or transceiver is correctly connected to the back of
your PC, then check the integrity of the Ethernet wire according
to Ethernet specifications. There could be a short circuit in the
wire, but the usual cause is that the wire has been disconnected
somewhere.


No internal TCP ports available

Cause:
You are trying to do too many activities at the same time, or some
combination of your activities has not closed the TCP sessions
correctly. This will happen if you open too many sessions to other
computers.

Solution:
Close some of your existing sessions. If necessary, exit the
program by logging off of all of the other computers, then restart
NCSA Telnet.


Packet received for invalid port -- reset sent

Cause:
Some other computer is sending you packets that NCSA Telnet does
not expect or understand. This often happens when you press ALT-F3
to exit NCSA Telnet and then start it back up again. It can happen
under a variety of network breakdown conditions.

Solution:
Do not press ALT-F3 to exit NCSA Telnet. If you already have, or
some other network breakdown caused the problem, the other
computer will eventually time out and stop sending you the extra
packets. If you continue to receive them, notify your system
administrator.


Reset received: syn sent

Cause:
The machine to which you are attempting to connect is refusing
your telnet connection.

Solution:
Check to see why that machine is not up and running. If it is,
check your configuration file to see if you are using the correct
IP number.







APPENDIX B

NCSA TELNET COMMAND REFERENCE



Key(s)            Action

ALT-A            Adds a session

ALT-N            Next session

ALT-M            Message screen

ALT-E            Escapes to DOS shell

ALT-G            Graphics menu

ALT-C            Capture file toggled on/off

ALT-R            Resets VT102 screen

ALT-H            Help screen

ALT-T            Starts file transfer as if typed: ftp [internet
address]

ALT-I            Sends internet address to host as if typed

ALT-S            Skips scroll, jumps ahead

ALT-P            Changes a parameter; one of: color, capture file
            name, backspace, session name, screen mode

ALT-F3            Aborts NCSA Telnet completely. Strongly discouraged

ALT-Y            Interrupts process

ALT-O            Aborts output

ALT-Q            Are you there?

ALT-U            Erases line

ALT-K            Erases character

Key(s)            Action

ALT-X            Closes connection

HOME            Exits graphics mode

CTRL-HOME        Clears/enters graphics mode

SCR LOCK        Pauses/restarts screen (do not use CTRL-NUM LOCK)

SCR LOCK        Enters/exits scrollback mode







APPENDIX C

CONFIGURATION FILE SUMMARY


This appendix contains a quick reference list of the keyword values
which are allowed in a NCSA Telnet configuration file.  There are two
sections, the first list contains the PC configuration entries which
apply to the overall program or to all sessions.  The second section
contains the list of attributes which may be assigned to individual
sessions.  Each keyword has an example value and a one-line summary of
its purpose.  For details on allowed values, see Chapter 6,
Installation and Configuration.  A template CONFIG.TEL file is included
on the distribution disk.



LOCAL CONFIGURATION


myip=10.0.0.51        IP address to use for the PC.
myip=RARP        Query the RARP server for my IP address.
netmask=255.255.255.0    Subnet mask for your local network.
arptime=3        Local network timeout for ARP requests.
domain="ncsa.uiuc.edu"    Default domain suffix.
domaintime=2        Domain lookup timeout per retry.
domainretry=4        Number of times to query domain nameserver(s).
tek=yes            Enable/Disable Tektronix graphics mode.
video=ega        Video display to use: cga, ega, hercules, no9.

bios=no            Use BIOS or write directly to screen.
hardware=3C501        Type of Ethernet hardware to use:
            3C501, PCNIC, NI5210, WD8003, 3C523, NICPS2
interrupt=3        Interrupt number for 3C501 board.
address=d000        Segment address of the Ethernet board's shared
            memory in hex.
ioaddr=360        I/O base address of the Ethernet board in hex.
ftp=yes            FTP server enable/disable, default is yes.
rcp=yes            rcp server enable/disable, default is yes.
capfile="\mycapture"    Specify a name for the capture file.
capfile=prn        Capture file is printer device (PRN).
hpfile=hp.out        HPGL codes for graphics go to this filename.
hpfile=COM1        HP plotter attached to COM1.
psfile=ps.out        Filename for PostScript output.
tekfile=tek.out        Filename for Tektronix 4014 codes when output
to disk.
passfile="\mypasswd"    Filename for FTP usernames and passwords.



HOST-SPECIFIC PARAMETERS


NOTE: The keyword name is special because it separates entries.

name=nic        Session name, separates lists of parameters for
            sessions.
host=sri-nic.arpa    Hostname or alternate name. Usually full domain name.
hostip=10.0.0.51    IP address of the host. Required if nameserver not used.
copyfrom=nic        Copy all missing parameters from a previous session.
gateway=1        Gateway precedence, starts at 1, goes up by ones.
nameserver=1        Nameserver precedence, starts at 1, goes up by ones.
nfcolor=white        Normal, foreground color.
nbcolor=black        Normal, background color.
rfcolor=black        Reverse, foreground color.
rbcolor=white        Reverse, background color.
ufcolor=blue        Underline, foreground color.
ubcolor=black        Underline, background color.
            Black, blue, green, cyan, red, magenta, yellow, or
            white.
scrollback=100        Number of lines of scrollback for this session.
clearsave=yes        Save cleared screen into scrollback region.
erase=delete        BACKSPACE key is set to "backspace" or "delete".
crmap=4.3BSDCRNUL    Use a different set of codes for carriage return.
duplex=half        Local echo, but sends all characters immediately.
contime=10        Connection timeout in seconds.
retrans=7        Initial retransmit timeout in 18ths of a second.
mtu=512            Limit on outgoing packet size.
maxseg=512        Limit on incoming packet size, given as TCP MSS option.
rwin=512        TCP receive window, can make up for low performance
            hardware.







BUGS AND SUGGESTIONS



We would appreciate notification of any bugs you have found and
suggestions that you might have.  You may send an electronic mail
message to (Internet format):

[e-mail]

or send this report by mail to:

NCSA TELBUG
152 Computing Applications Building
605 E. Springfield Ave.
Champaign, Illinois 61820

Name:

Installation:

Address (Electronic):


Address (U.S. Mail):





Telephone:  (        )             -

Version of NCSA Telnet and IBM System software:

Description of Problem/Suggestion: