Configuring the TN3270 Telnet Server to access the terminal LUs

One way to enable this support is to set up a new TN3270 telnet port. The following instructions guide you through setting up a new port and the changes you must make to the PROFILE.TCPIP data set. The examples in Configuring the TN3270 Telnet Server show several variations of this support.

1. Select an unused port, such as 2023. If you have a firewall installed, ensure that this port is allowed through the firewall.
2. Do one of the following steps:
   • If you are running the TN3270 Telnet Server in a separate address space (optional on z/OS Communications Server Version 1.6 through 1.8, required on Version 1.9 or later), specify a PORT num TCP jobname NOAUTOLOG statement to reserve the new port for the TN3270 Telnet Server.
   • If you are running the TN3270 Telnet Server in the TCP/IP address space, specify a PORT num TCP INTCLIEN statement to reserve the new port for the TN3270 Telnet Server.
3. Create a new set of TELNETPARMS and BEGINVTAM blocks for the new port by copying the existing TELNETPARMS and BEGINVTAM blocks for port 23.
4. Customize the new TELNETPARMS and BEGINVTAM blocks to use this new port number. Ensure that the previous TELNETPARMS and BEGINVTAM blocks also specify a port number (typically 23).
5. Make the following changes to your new BEGINVTAM block:
   1. If you intend to use this new port for only z/OS Debugger in full-screen mode using a dedicated terminal, you can remove all the statements from the BEGINVTAM block that you created in step 3, except the PORT statement. Go to step 5c.
   2. Remove any copied DEFAULTLUS, DEFAULTLUSSPEC, DEFAULTAPPL and LUMAP statements.
   3. Specify a new LUGROUP specification that indicates which terminal LUs that will be used as dedicated terminals for debugging in full-screen mode using a dedicated terminal. These terminal LUs must have a DLOGMOD specification in their APPL definition statement.
   4. Specify some client_identification statements (such as HNGROUP and IPGROUP).
   5. Specify a new LUMAP statement with KEEPOPEN (along with the proper LU group operand and client_identification operand).

      The KEEPOPEN operand forces the TN3270 Telnet Server to keep the access control block (ACB) for the LU open at all times (for those LUs affected by this LUMAP statement). With the ACB open, z/OS Debugger can acquire the LU if the LU is connected to a client terminal emulator session but is not in session.

   6. Specify a new ALLOWAPPL EQAMV* statement (or ALLOWAPPL * if site policies allow it) in the BEGINVTAM block to let z/OS Debugger start a session with the terminal LU.

      If you defined the name that z/OS Debugger uses for its side of the VTAM session with a name other than EQAMVnnn, then you should specify that name on the ALLOWAPPL statement, rather than EQAMVnnn. (Or just use * if your site policies allow it.)

   7. Specify whether the terminal is to display a session manager panel, a USSMSG10 panel, or a Telnet Solicitor Logon panel.

      The user must know what terminal LU they have acquired when they connect their terminal emulator session to this new port. If you normally use a session manager that displays the terminal LU, then you can continue to use that method. Otherwise, use one of the following panels:

      • A modified USSMSG10 panel that displays the terminal LU name
      • The Telnet Solicitor Logon panel, if the terminal emulator itself shows the terminal LU name

      To specify which panel is to be displayed, do the following steps:

      1. To display a session manager panel, specify the FIRSTONLY operand on a DEFAULTAPPL statement that defines the session manager to run. To use the LU to debug a program in full-screen mode using a dedicated terminal, the user must first exit the session manager panel and return to the Telnet Solicitor Logon panel.
      2. To display a USSMSG10 panel, specify a USSTCP statement. If your terminal emulator session supports the TN3270E protocol, the USSMSG10 panel can be customized to display the terminal LU name. See the IBM Communication Server IP Configuration Reference manual for information about how to create a new USS table load module that contains a USSMSG10 panel which includes the @@LUNAME parameter.
      3. To display a Telnet Solicitor Logon panel, code no additional statements.

If you want to restrict access for a terminal connected to this new port so that no one can use it to start any application and that no application other than z/OS Debugger can acquire it, then do the following steps:

1. Remove any statements from the port's BEGINVTAM block other than those recommended above.
2. Write only one ALLOWAPPL statement, specifying EQAMVnnn or, if you didn't use EQAMVnnn, the minor node name that z/OS Debugger uses for its side of the VTAM session.
3. Use the USSMSG10 panel or Telnet Solicitor Logon Panel display method.

After you make these changes to the TCP/IP configuration data set, you must instruct TCP/IP to use this updated definition and start the new port. The Telnet server uses the VARY command to change Telnet functions. One of the following commands can help you change Telnet functions:

VARY TCPIP,,OBEYFILE

To start, restart or change a port by updating the Telnet profile. If you are running a TN3270 Telnet Server in a separate address space, you need to include the TN3270 Telnet Server jobname in the command. For example, VARY TCPIP,jobname,OBEYFILE.

VARY TCPIP,,TELNET,STOP and VARY TCPIP,,OBEYFILE

To stop a Telnet port, and then restart that port or a new port without stopping the TCP/IP stack.

See IBM Communication Server IP Configuration Reference for more information about the VARY TCPIP command.

After making these changes, your users can set up a unique terminal emulator session that connects to this new port, and debug programs that require the use of full-screen mode using a dedicated terminal.