Using the PAD

This section discusses starting an X.28/X.3 terminal PAD session. For information on how to start X.29 on the system, refer to "Managing the Triple-X PAD".

To start a terminal PAD session, run the xspad command. On systems where the PAD is configured this starts a terminal PAD session and provides the PAD prompt ( *, the asterisk character). Enter the PAD commands at the PAD prompt.

To start a PAD session:

1. Ensure the PAD is configured on the system.
2. Run xspad -l sx25a# where # is the port number.
3. Issue the call to the remote X.25 host at the PAD prompt.
4. Log on to the X.25 host and run the desired application.

For more information, see the xspad Command in Appendix A.

Commands

Once connected to an X.3/X.28 terminal PAD session, various commands can be issued to the PAD. Some of these commands can only be issued after a connection has been established with the remote X.25 host. Based on the PAD's profile, the commands understood by the PAD are either based on the CCITT standard or can be in a less cryptic style (advanced mode).

The start/stop DTE user may interact with the PAD using PAD commands. These commands provide:

• Establishment and clearing of virtual calls.
• Selection of PAD profiles.
• Display of the PAD parameter values.
• Changing the PAD parameter values.
• Sending an interrupt or a reset packet.

To enter a PAD command at the terminal, the user enters the command at the PAD prompt. As long as there is not a remote host connection, the current prompt is the PAD prompt ( *, the asterisk character). To get to the prompt when connected to a remote session, press Ctrl-P.

At the prompt, the following commands can be issued:

set 2:1, 14:2
or in advanced mode
set echo:1, lfpad:2

Establishing Calls

To establish a connection with a remote X.25 host, a call must be made to it. The call must be given the remote DTE's address and any call user data or facilities being requested.

Example Calls

The following are typical calls that might be made from the PAD command prompt:

Connected Sessions

After a call has been placed to the remote X.25 host, it can be rejected by the network, or the remote host, or accepted by the remote host. If rejected, a clear packet is received and results in a message similar to those described in "Ending Calls". Once connected, the terminal is under the control of the TTY system of the remote host. Typically a login screen is presented. After the user has logged in, it can be used the same as other attached TTYs.

Once a session is established, the TERM type and stty settings should be verified. The TERM type should be set to the type of terminal you are using, for example, TERM=aixterm . The stty settings can be verified with stty -a . The row and column attributes need to be updated if using X-Windows and the size of the window is not equal to 80x25 (default setting). The echo, echoe, and echok attributes might also need to be turned

On/Off

To change an stty attribute, enter one of the following commands:

stty echo (turns echo on)

stty -echo (turns echo off)

stty 50 rows (updates the row setting to 50)

Ending Calls

Once a connection is established, there are a number of ways in which it can be terminated. Termination of the login shell used to log in to the remote X.25 host closes the connection and results in a message such as the following:

CLEAR DTE 0 241 - Call cleared, by remote device, data may be lost

As the session was terminated above the PAD layer, the PAD code did not expect it and so could not tell if it was user-initiated or not. If it was user-initiated, then no data was lost.

An alternative is to press Ctrl-P to get to the PAD command prompt, and then enter iclear. The iclear command causes the local terminal PAD to send a request to the host PAD to clear the connection. The host PAD software then issues the clear, but without regard for any applications that might be running on the remote host under this login. As the remote PAD software issues the command to clear the connection, the diagnostic software is likely to reflect this as being an expected clear.

CLEAR PAD 0 0 - Call cleared, remote request

The additional text is given when advanced mode is enabled through the profile; otherwise the base clearing reason is given.

Exiting xspad

From the PAD command prompt that is reached by ending the call as described above, enter ^k (Ctrl-K) to terminate the xspad program. The xspad application must not have a call established when attempting to terminate xspad.

Automatic Termination and Identification for AIXLink/X.25 1.1.3 (and later)

The PAD application is automatically exited upon termination of the X.25 Host connection. This optional feature is enabled using the -x flag with the xspad command (for example, xspad -x -l sx25a0 ).

The PAD default is to enter ^k (Ctrl-K) before exiting. If an X.25 Host connection terminates and the user does not exit, the user can initiate another X.25 connection using the same X.28 STREAMs connection.

Note: This feature applies only to xspad (the user space PAD application).

Getting Help

Help is provided through the help command. To list the help topics, enter help list . Each of the PAD commands has help text associated with it (for example, help call) . Also each PAD parameter and profile has help text. The language in which the text is displayed can be changed using the language command.

Clearing Codes

When the call is cleared, the information passed in the X.25 clear packet is displayed. When advanced mode has been selected through use of the appropriate profile, a more detailed text explanation of the clear is given. Otherwise, the base cause is displayed as follows:

PAD Parameters

The operation of the PAD depends on the value of a set of internal variables called PAD parameters. An independent set of parameters exists for each start/stop mode DTE. The current value of each PAD parameter defines the operational characteristic of the related function.

Initially, the values of the parameters are chosen by selecting one of the available profiles. Subsequent changes for a given terminal session are done under control of the session's TTY subsystem on the host PAD. When the application being run requires a change to the terminal characteristics, it modifies the session's stty structure which in turn causes the X.29 protocol to issue a change to the session's X.3 parameters held in the terminal PAD.

The following is a list of the X.3 PAD parameters:

par 1

PAD Recall

This parameter specifies the character that you can type at the terminal to interrupt data flow with the X.25 host (in order to enter commands addressed to the PAD). Possible values are:

Note: If you set this parameter to 0, you will not be able to change the PAD parameters any further.

Note: When working in line mode, this parameter should be set to 1 to get an echo from the PAD, and the echo provided by the host should be disabled with the command stty -echo.

If this parameter is set to 0, every character typed at the terminal is sent by the PAD in an individual packet. For the other values, the PAD acts as a buffer and sends a packet only when the specified character is entered. If you are working on your terminal in line mode, entering UNIX commands for example, you may set this parameter to 18 and packets will be sent to the host only when you press Enter, Ctrl-C, or Ctrl-D.

Note: If parameters 5, 12, or 22 is set to a non-zero value, the characters XON and XOFF are NOT echoed.

PAD Profiles

Within the terminal PAD, there are four available profiles. Which profile is loaded for a particular session is controlled by the PROF command. The command to list what profiles are available is help prof. By default, the PROFILE_51 profile is used.

The following profiles are implemented:

The settings of the X.3 parameters for each of the profiles are: