HP OpenVMS Systems Documentation

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, enter either the DISCONNECT or the close command.

The following example shows two ways to close connections:

% logout
%TELNET-S-REMCLOSED, Remote connection closed
-TELNET-I-SESSION, Session 01, host galaxy, port 23
TELNET>

TELNET> EXIT
$
% [Ctrl/]] (characters not echoed)
TELNET> DISCONNECT
galaxy.udp.com>
TELNET> DISCONNECT
%TELNET-S-LCLCLOSED, Local connection closed
-TELNET-I-SESSION, Session 01, host galaxy, port 23
TELNET>

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

With DCL command files, you can start TELNET and TN3270 sessions (see Section 4.6.1) and customize the TELNET/TN3270 environment (see Section 4.6.2).

4.6.1 Starting TELNET/TN3270

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

The following 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

You can create initialization command files to customize your TELNET/TN3270 sessions with SET, ENABLE, and DISABLE commands. These command files:

• Are optional. They eliminate the need to enter 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.
• Let you specify the logical name, TELNETINIT, to point to an initialization file.

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"

During a session with a remote host, you can toggle 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), enter 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, enter 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, enter 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/]]  (characters not echoed)
TELNET> SHOW STATUS
Session  1 Active  Host biway Port 23
    Operating Mode: Character-at-a-time
    Escape character: '^]'
    Options:
       Echo - Remote
       Terminal Type - Local
       Terminal Type - VT300
       Suppress Go Ahead - Local
       Suppress Go Ahead - Remote
    Terminal Dataoveruns:    0
    Suspended Network I/Os:  0

   .
   .
   .
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 incorrectly enters 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 host to which BENTLEY connected most recently is sands . However, because BENTLEY incorrectly typed the password during login, sands closed the TELNET connection and displayed the following:

     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/]]   (characters not echoed)

TELNET> SHOW STATUS
Session  1 Active  Host FERN
   .
   .
   .
TELNET> CONNECT GANNET
   .
   .
   .
gannet> [Ctrl/]] (characters not echoed)
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 '^]'.
   .
   .
   .


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/]]   (characters not echoed)
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 and then returns to the TELNET session.

TELNET> SPAWN
$ DIR
   .
   .
   .
$ DEL TR3.TXT:*
$ LOGOUT
Process FERN_1 logged out at 17-JAN-2002 11:08:24.90
TELNET>

TELNET supports:

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

The TELNET command SHOW STATUS helps you keep track of multiple sessions. The SHOW STATUS display uses the terms shown in Table 4-2.

TELNET> RESUME
n

TELNET> RESUME
n

To open another TELNET connection, perform the following steps:

1. At the system prompt of the remote host, enter 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
   .
   .
   .
finder> ()
   .
   .
   .
finder> [Ctrl/]]     (characters not echoed)
TELNET> CONNECT KEEPER
   .
   .
   .
keeper> ()
   .
   .
   .
keeper> [Ctrl/]]     (characters not echoed)
TELNET> ()

To toggle between one open TELNET connection and another:

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

For an example, see Section 4.7.

4.9.2 Displaying Session Information

To display a list of your active sessions, use the following 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, use the ENABLE, DISABLE, and SET commands. You can modify how TELNET and TN3270 perform the following actions:

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

You can redefine the following control characters, in situations when, for example, 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. Alternatively, you can redefine a key interactively by using the DEF KEY function (Ctrl/K on VT100-and VT200-series terminals) (see Section 4.12.9.)

You can determine the mode TELNET uses to transmit data. The appropriate TELNET mode for a session depends on:

• The remote host to which you are connecting
• The applications you use

Table 4-3 shows the modes that control TELNET communications.

While in input mode (an active session with a remote host), you can enter SEND commands that affect the remote host's processing of commands you have entered. You use these commands when the remote host does not recognize the default key or key sequence used for the same operation. You can use the SEND AYT and SEND NOP commands to determine whether or not your session with the remote host is still open. Table 4-4 lists the functions available to you at the remote host with each SEND command.

You can run a TELNET session with a host that uses IBM 3270 model terminals by using the TN3270 command. The TN3270 command:

• Provides IBM 3270 Information Display System (IDS) terminal emulation.
• Assigns IBM 3270 functions to your keyboard.
• Assigns IDS functions to specific keys.

During a TN3270 session, you can do the following:

• Record your sessions ( Section 4.12.5).
• Redefine keys permanently ( Section 4.12.9.5).
• Redefine keys interactively ( Section 4.12.9.5.1).
• Troubleshoot problems ( Section 4.12.9.6).

Table 4-5 lists the IBM 3270 terminal models that TELNET/TN3270 can emulate.

When you use TELNET and specify IBM 3270 model terminal emulation (TN3270), the image displayed on your screen depends on the following criteria:

• The type of terminal that you are using or that your PC is emulating
• The features you set on it

Sections 4.12.2.1 and 4.12.2.2 explain how to set up VT200- and VT100-series terminals (or emulation on PCs), respectively.

4.12.2.1 VT200-Series Terminal Setup

To set up a VT200-Series terminal for emulation, follow these steps:

1. At the Set-up Directory menu, select the keyboard type that corresponds to the keyboard layout you are using (for example, North American).
2. At the Display Set-up menu, select the following:
   • Interpret controls
   • Light text, dark screen
   • Cursor (visible)
3. At the General Set-up menu, select the following:
   • VT200 or VT100 mode (if VT100 mode, set VT100 ID)
   • 7-bit or 8-bit controls
   • Multinational/national
   • Normal cursor keys
   • No new line
4. At the Communications Set-up menu, select the following:
   • XOFF at 64 or XOFF at 128
   • 8-bit communication line
   • 8-bit (any) parity
   • No local echo
5. At the Keyboard Set-up menu, select warning bell ON.

At the DCL prompt, enter the following command:

 $  SET TERMINAL /INQUIRE

The software determines the terminal's characteristics and sets the appropriate parameters.

If you select National character mode, enter the following command:

$ SET TERMINAL /NOEIGHTBIT