DIGITAL TCP/IP Services for OpenVMS
User's Guide

A user sends the man cp command to UNIX host hence for execution. #2

$ RSH /USER_NAME=ROGERS DELPHI LS 

OpenVMS user PHILIPS issues the ls command for execution at remote UNIX host delphi. PHILIPS is accessing an account called rogers.

$ RSH /PASSWORD=BLOOMER AVOC8N DIRECTORY 

OpenVMS user PANTO sends the DIRECTORY command to remote OpenVMS host AVOC8N. The remote directory listing is of PANTO's home directory.

RSH /PASSWORD invokes REXEC, which authenticates PANTO's remote password.

$ RSH /PASSWORD MAGIC CAT BUZZ.TXT 
REXEC password:        (not echoed)[Return] 
 

A user sends the cat command to host magic. /PASSWORD invokes REXEC, which requires a password. Because the password was omitted from the command line, REXEC prompts the user for it.

With the TELNET software in DIGITAL TCP/IP Services for OpenVMS (UCX), you can log into a remote internet system. This is called establishing a TELNET session. Your terminal appears to be attached directly to the remote system. Using the TN3270 command, you can run a TELNET session with a host that uses IBM 3270 model terminals.

Note that you can also use RLOGIN to log into remote internet hosts. To determine the best remote login service to use for your needs, see Section 1.1.2. For more information about RLOGIN, see Chapter 4.

What You Can Do

The following table lists the TELNET/TN3270 network terminal services and the sections that explain how to use them.

Capability	Section
Use either DCL-style or UNIX-style command syntax	5.1
Establish a network terminal session with a UNIX host or another OpenVMS host	5.3
Log all terminal output to a file	5.5
Toggle between the remote host and the local TELNET prompt	5.7
Suspend TELNET/TN3270 to spawn a subprocess at the DCL prompt	5.8
Establish multiple sessions	5.9
Toggle between open sessions	5.9.1
Customize the way TELNET interprets control characters, sends and receives transmissions, and displays processing on your terminal	5.6.2 5.10
Send commands to the remote host that affect processing of commands you have entered	5.11
Run IBM 3270 model terminal emulation (TN3270)	5.12
Record a TN3270 screen's contents	5.12.6

What You Need

To use the network terminal services, you need the following:

• A user account on the remote host also running TELNET.
• A user account on the OpenVMS system that runs DIGITAL TCP/IP Services for OpenVMS.

Command Summary

To use TELNET, issue the commands summarized in Table 5-1 (for complete command descriptions, see Section 5.13).

Table 5-1 TELNET/TN3270 Commands: Summary

DCL-Style	UNIX-Style	Description
Starting (at the DCL Prompt)
TELNET	telnet	Invokes TELNET
TELNET remote_host	telnet remote_host	Invokes TELNET and establishes a connection to a remote host
TN3270	N/A	Invokes TELNET and TN3270
TN3270 remote_host	N/A	Invokes TELNET, runs TN3270, and establishes a connection to a remote host
Getting In and Out of Sessions
CONNECT	open	Establishes a connection between the local host and a remote host
CREATE_SESSION	N/A	Establishes a pseudodevice and connects it to a remote listener port
DELETE_SESSION	N/A	Deletes a pseudodevice created by the CREATE_SESSION command
DISCONNECT	close	Terminates your current session
Ctrl/]	Ctrl/]	Takes you from the remote host back to the TELNET prompt
EXIT	quit	Closes open connections and exits from TELNET
HELP	help ?	Invokes online help
RESUME	[Return]	Resumes an open connection
SPAWN	z	Suspends your TELNET session and takes you to the DCL prompt
Customizing the TELNET Environment
DISABLE AUTOFLUSH	toggle autoflush	Disables the automatic flushing of output when interrupt characters are sent
DISABLE AUTOSYNCH	toggle autosynch	Disables the automatic sending of interrupt characters in urgent mode
DISABLE BINARY	toggle binary	Disables transmission in binary mode
DISABLE CRLF	toggle crlf	Disables the sending of carriage returns as Return LF
DISABLE CRMOD	toggle crmod	Disables the mapping of received carriage returns
DISABLE DEBUG	toggle netdata	Disables the display of data flow information in hexadecimal
DISABLE LOCAL_CHARS	toggle localchars	Disables the interpretation of certain control characters by your local TELNET client and passes them to the remote TELNET server
DISABLE OPTIONS_VIEW	toggle options	Disables the display of option negotiations between the client and server
ENABLE AUTOFLUSH	toggle autoflush	Enables the automatic flushing of output when interrupt characters are sent
ENABLE AUTOSYNCH	toggle autosynch	Enables the automatic sending of interrupt characters in urgent mode
ENABLE BINARY	toggle binary	Enables transmission in binary mode
ENABLE CRLF	toggle crlf	Enables the sending of carriage returns as Return LF
ENABLE CRMOD	toggle crmod	Enables the mapping of received carriage returns
ENABLE DEBUG	toggle netdata	Enables the display of data flow information in hexadecimal
ENABLE LOCAL_CHARS	toggle localchars	Enables the interpretation of certain control characters by your local TELNET client and prohibits them from being passed to the remote TELNET server
ENABLE OPTIONS_VIEW	toggle options	Enables the display of option negotiations between the client and server
SHOW PARAMETERS	display	Displays the current parameter settings
SHOW SESSION		Displays the current sessions
SHOW STATUS	status	Displays the current status
SET ECHO	set echo	Sets the echo character to the specified character
SET ERASE	set erase	Sets the erase character to the specified character
SET ESCAPE	set escape	Sets the escape character to the specified character
SET FLUSHOUTPUT	set flushoutput	Sets the flush output character to the specified character
SET INTERRUPT	set interrupt	Sets the interrupt character to the specified character
SET KILL	set kill	Sets the kill character to the specified character
Customizing the TELNET Environment (Cont.)
SET MODE	mode	Sets the transmission mode to character or line
SET QUIT	set quit	Sets the quit character (an alternate interrupt character) to the specified character
SET TERMINAL		Sets the terminal type to the specified model
Sending Commands to the Remote Host
SEND AO	send ao	Sends the Abort Output command
SEND AYT	send ayt	Sends the Are You There command, testing the path to the remote application and eliciting connection status information from the remote host
SEND BRK	send brk	Sends the Break command
SEND EC	send ec	Sends the Erase Character command
SEND EL	send el	Sends the Erase Line command
SEND GA	send ga	Sends the Go Ahead command
SEND IP	send ip	Sends the Interrupt character
SEND NOP	send nop	Sends the No Operation command to test whether data can be sent to the remote host, eliciting an error if the connection is not open
SEND SYNCH	send synch	Sends the Synchronize character

5.1 Typing TELNET/TN3270 Commands

Use the following rules when you type a TELNET command line.

5.1.1 DCL and UNIX Command Formats

With the TELNET command and most of the commands at the TELNET prompt, you can use either DCL-style or UNIX-style syntax. For example, the following two commands produce the same results:

$ TELNET 
TELNET> SHOW PARAMETERS 

$ TELNET 
TELNET> DISPLAY 

No quotation marks are required for typing:

• The TELNET command line, for example:

  $ TELNET CENTRAL
  

• The TN3270 command line, for example:

  $ TN3270 CENTRAL 
  

• Commands at the TELNET prompt, for example:

  TELNET> CONNECT CENTRAL 
  

The following example connects to UNIX host migain and sets a terminal type with the /TERMINAL_TYPE qualifier. No quotation marks are needed to pass a terminal type to migain in lowercase, as demonstrated with the remote host's printenv command.

$ TELNET MIGAIN /TERMINAL_TYPE=vt300 
%TELNET-I-Trying, Trying ...11.90.208.56 
%TELNET-I-SESSION, Session 01, host migain, port 23 
-TELNET-I-Escape, Escape character is '^]' 
 
Hello from UNIX host migain 
 
login: root 
Password:...
   .
   .
   .
migain# printenv 
TERM=vt300 
HOME=/ 
SHELL=/bin/csh 
USER=root 
PATH=/bin:/usr/bin:/usr/ucb:/etc:/usr/etc:. 
LOGNAME=root 
PWD=/ 
migain# 

You can obtain online help for the TELNET and TN3270 services by typing one of the following commands:

$ HELP TCP_IP_SERVICES NETWORK_TERMINALS
$ HELP TCP_IP_SERVICES TELNET_COMMAND
$ HELP TCP_IP_SERVICES TN3270_COMMAND

You can also enter the HELP command at the TELNET prompt:

TELNET> HELP

You can start a TELNET or TN3270 session with a remote host (also called establishing a connection and opening a connection) in one of the following ways:

• At the DCL prompt, issue either the TELNET or TN3270 command and specify a remote host.
• At the DCL prompt, issue the TELNET or TN3270 command with no parameters. At the TELNET or TN3270 prompt that appears, issue the CONNECT or open command, specifying a remote host.
• Invoke and use TELNET or TN3270 from a command procedure (see Section 5.6.1).

The following example shows three ways to establish a connection interactively:

$ TELNET CENTRAL /TERMINAL_TYPE=IBM-3278-2 
 
 
$ TELNET 
TELNET> CONNECT CENTRAL 23 VT200
 
 
$ TN3270 CENTRAL /TERMINAL_TYPE=IBM-3278-3 

You can invoke TELNET or TN3270 and, without connecting to a remote host first, enter certain commands that customize the sessions and display parameters or status.

5.4 Exiting TELNET and TN3270

You can end a TELNET or TN3270 session (close the connection) in one of the following ways:

• At the remote host's system prompt, log out.
• At the remote host's system prompt, return to the TELNET or TN3270 prompt and disconnect the session, as follows:
  1. At the remote host's system prompt, press the TELNET/TN3270 escape character (Ctrl/] is the default).
  2. At the TELNET or TN3270 prompt, issue either DISCONNECT or close.

  The following example shows two ways to close connections:

  % logout 
  %TELNET-S-REMCLOSED, Remote connection closed 
  TELNET> EXIT 
  $ 
   
   
  % [Ctrl/]] 
  TELNET> DISCONNECT 
  %TELNET-S-REMCLOSED, Remote connection closed 
  TELNET> EXIT 
  $ 
  

  5.5 Keeping a Log of Your TELNET/TN3270 Session

  To keep a log of your TELNET session, use the /LOG_FILE qualifier. (You cannot use this qualifier with a TN3270 session.)

  The following example establishes a TELNET connection to node central, sets the terminal type to VT200, and logs all session output to the file CENT.LOG in your current directory.

  $  TELNET/LOG_FILE=CENT.LOG/TERMINAL_TYPE=VT200 CENTRAL
  

  5.6 Command Procedures

  With DCL command files, you can start TELNET and TN3270 sessions (see Section 5.6.1) and customize the TELNET/TN3270 environment (see Section 5.6.2).

  5.6.1 Starting TELNET/TN3270

  You can create a command procedure containing the DCL DEFINE and TELNET (or TN3270) commands.

  The following example shows an example of a TELNET command procedure.

  $! My TELNET startup command file, START_TELNET.COM. 
  $! 
  $! This command procedure establishes a TELNET session 
  $! with UNIX host central. 
  $! 
  $ DEFINE /USER_MODE SYS$INPUT TT: 
  $ TELNET CENTRAL 
  

  5.6.2 Initialization Command Files

  Initialization command files can customize your TELNET/TN3270 sessions with SET, ENABLE, and DISABLE commands. These command files:

  • Are optional. They eliminate the need to issue individual TELNET commands.
  • Have the following requirements:
    • Location: Your login directory
    • Name: TELNETINIT.INI
    • Format: one command per line
  • Run automatically when you invoke TELNET or TN3270.

  The following example shows a TELNET initialization command procedure.

  ! This file, TELNETINIT.INI, sets my TELNET parameters 
  ! the way I like them. 
  ! 
  DISABLE AUTOFLUSH 
  ENABLE BINARY 
  ENABLE DEBUG 
  SET DEVICE /TERMINAL=VT300 
  SET ESCAPE "^p" 
  

  5.7 Toggling Between the Remote Host and Local TELNET/TN3270

  During a session with a remote host, you can toggle back and forth between the local TELNET or TN3270 process and the connected host. For example, at the TELNET prompt, you might want to display status, modify a TELNET parameter, or spawn a DCL subprocess.

  • To return to the local TELNET or TN3270 prompt (TELNET command mode), type the TELNET escape sequence (the default is Ctrl/]) at the remote host's prompt (TELNET input mode).
  • To resume your session with the remote host, type one of the following at the TELNET (or TN3270) prompt.

    TELNET> [Return]
    

    
    or

    TELNET> RESUME 
    

    
    or

    TELNET> RESUME n 
    

    
    where n is the number of the session to which you want to return.
  • To change the default escape sequence, type the following at the TELNET (or TN3270) prompt:

    TELNET> SET ESCAPE escape_character
    

  The following example toggles between remote UNIX host biway and the local OpenVMS system.

  biway> [Ctrl/]] 
  TELNET> SHOW STATUS 
  Session  1 Active  Host BIWAY 
  Operating Mode: 
  Character-at-a-time 
  Escape character: '^]' 
  Options:
     .
     .
     .
  TELNET> [Return] 
  biway>
  

  In the next example, user BENTLEY, working at OpenVMS node EAGLE, uses TELNET to do the following:

  1. Establish a connection to UNIX host fern.
  2. Return to the local TELNET prompt.
  3. Display status.
  4. Establish a connection to host gannet.
  5. Return to the TELNET prompt.
  6. Display status.
  7. Connect to sands. But, sands closes the connection because BENTLEY mistypes the password three times.
  8. Try to resume the session with gannet. However, RESUME without specifying a session number fails:
     • With multiple sessions, RESUME's default is the "active" session, the one with the most recently opened connection.
     • The most recent host to which BENTLEY connected is sands. However, due to BENTLEY's mistyping of the password during login, sands closed the TELNET connection. Thus, TELNET displays "No current session."
     • Because no connection is "active" (or "current"), BENTLEY must specify a session number on the RESUME command line.

$ TELNET FERN 
   .
   .
   .
fern> [Ctrl/]]
 
TELNET> SHOW STATUS  
Session  1 Active  Host FERN 
   .
   .
   .
TELNET> CONNECT GANNET 
   .
   .
   .
gannet> [Ctrl/]] 
 
TELNET> SHOW STATUS 
Session  2 Active  Host GANNET 
    Operating Mode: Character-at-a-time 
    Escape character: '^]'
   .
   .
   .
Session  1 Waiting Host FERN 
 
TELNET> CONNECT SANDS 
%TELNET-I-Trying, Trying...11.18.222.95 
%TELNET-I-SESSION, Session 03, host sands, port 23 
-TELNET-I-Escape, Escape character is '^]'.
   .
   .
   .
      Sun Microsystems, Inc. UNIX System sands - Authorized Access Only 
 
Username: BENTLEY 
Password: 
User authorization failure 
Username: BENTLEY 
Password: 
User authorization failure 
Username: BENTLEY 
Password: 
User authorization failure 
 
Remote connection closed 
 
TELNET> RESUME 
No current session 
TELNET> SHOW STATUS 
Session  1 Waiting Host FERN 
Session  2 Waiting Host GANNET
   .
   .
   .
TELNET> RESUME 2 
 
gannet> [Ctrl/]] 
TELNET> SHOW STATUS 
Session  2 Active  Host GANNET 
    Operating Mode: Character-at-a-time 
    Escape character: '^]'
   .
   .
   .
Session  1 Waiting Host FERN 
TELNET>

While using TELNET, you can use the SPAWN command to suspend your current session and create a subprocess at the local DCL prompt. At the DCL prompt, you can then enter any number of DCL commands. To return to your suspended TELNET session (exiting the DCL subprocess), enter the LOGOUT command. In the following example, the user suspends the TELNET session to list the files in the working directory on the local host and deletes one of the files in that directory.

TELNET> SPAWN
$ DIR
   .
   .
   .
$ DEL TR3.TXT:*

TELNET supports:

• Multiple simultaneous connections
• Up to 10 simultaneous sessions
• Only one session at a time if it uses TN3270

The TELNET SHOW STATUS command helps you keep track of multiple sessions. The SHOW STATUS display uses the terms shown in Table 5-2.

Table 5-2 TELNET SHOW STATUS Display: Terminology

Term	Meaning
Active host	Host from which you typed the escape sequence to return to the TELNET prompt.
Current session	If you log out of the active host at its system prompt, or issue the TELNET DISCONNECT command, no current session exists. To resume a connection, even if only one exists, issue: TELNET> RESUME n
Waiting hosts	Other hosts with whom you have open sessions, numbered in the order that you connected to them. To resume a connection with a waiting host, even if only one exists, issue: TELNET> RESUME n

To open another TELNET connection:

1. At the system prompt of the remote host, press the TELNET escape sequence (default is Ctrl/]).
2. TELNET returns to the TELNET prompt.
3. Start another session by issuing the CONNECT command.

The following example starts multiple sessions with UNIX hosts finder and keeper.

$ TELNET FINDER /TERMINAL_TYPE=IBM-3278-2 
   .
   .
   .
finder> 
   .
   .
   .
finder> [Ctrl/]] 
TELNET> CONNECT KEEPER 
   .
   .
   .
keeper> 
   .
   .
   .
keeper> [Ctrl/]] 
TELNET> 

To toggle from one open TELNET connection to another:

1. Type the TELNET escape sequence.
2. If necessary, issue SHOW STATUS to check the number of your session with the other host.
3. Issue the TELNET RESUME n command, where n is the number of the session to which you want to return.

For an example, see Section 5.7.

5.9.2 Displaying Session Information

To display a list of your active sessions, use the SHOW SESSION command:

TELNET>  SHOW SESSION [Return]
Session 01, host finder, port 23
Session 02, host keeper, port 23 (default active session)

If there are no active connections, the SHOW SESSION command displays the following message:

%TELNET-E-NOSESSION, No active session

To customize the TELNET/TN3270 processing environment, issue ENABLE, DISABLE, and SET commands. You can modify how TELNET and TN3270:

• Send and receive transmissions
• Display processing on your terminal
• Interpret certain control characters

You can redefine the following control characters, such as when your terminal or the remote host does not recognize the corresponding default control character.

• Echo
• Erase
• Escape
• Flush output
• Interrupt
• Kill
• Quit

Use the SET command to redefine these characters. For example, the following command defines the interrupt character to be the letter a or A.

TELNET> SET INTERRUPT "^a" 

TN3270 allows you to redefine your keyboard. You can redefine most IBM 3270 model functions and all emulated functions and characters. You can create a key definition file with DEFINE/KEY statements to redefine the keyboard. Or, you can redefine a key interactively, using the DEF KEY function (Ctrl/K on VT100- and VT200-series terminals). (See Section 5.12.10.)