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7318 Model S20 Guide and Reference

Adding Dynamic Sessions

The Transmission Control Protocol/Internet Protocol (TCP/IP) feature of the Model S20 enables terminal users to log in to any system on the local area network (LAN) to which the 7318 is connected. The LAN must support the TCP/IP protocol suite and the telnet and rlogin virtual terminal protocols. Since these protocols are widely implemented across a broad range of both AIX and non-AIX computer systems, the S20 considerably expands the facilities available to you.

The Model S20 provides three commands for accessing remote systems. These commands are telnet, rlogin, and tn3270. They are based directly on the AIX commands.

For terminals connected directly to the 7318, this feature provides the ability to conduct multiple terminal sessions with one or more host computers simultaneously.

Once you have logged in to a port that is configured for a command session, you may initiate up to six additional dynamic sessions with the telnet, rlogin, and tn3270 commands. These commands give you a facility to interact with multiple host computers simultaneously, using a variety of virtual terminal interfaces, as follows:

You can maintain all three sessions simultaneously and switch between the three sessions using a hot-key sequence.

The model S20 supports up to seven simultaneous sessions per serial port. Following are the total number of simultaneous sessions for each model S20 where all sessions are the same application type:

Session Application Maximum Simultaneous Sessions for Each S20
rlogin or krlogin 80
telnet 48
tn3270 16 (terminal screen size 24 x 80)
SLIP and PPP 16
P10 style native session 112 (not including transparent print)
Note: Applications that do not allow multiple sessions (PPP, SLIP, Rtelnet, and P10 style) use the equivalent of five rlogin sessions, five krlogin sessions, three telnet sessions, or one tn3270 session.


  1. You must be in password privilege mode on the 7318.
  2. You must have root user authority.


The 7318 Model S20 can support up to seven dynamic sessions without transparent print and six if you are using transparent print. The default configuration file provides four dynamic sessions. The following procedure explains how to add dynamic sessions to the default configuration file.

  1. If the configuration file is not already customized for the 7318, copy the /usr/lib/cns/s20.cfg file to a file named /usr/lib/cns/XXXXXXXXXXXX.cfg, where the XXXXXXXXXXXX parameter is the Ethernet address of the specified 7318.
  2. Using your favorite editor, find the [Session] section within the XXXXXXXXXXXX.cfg file.
  3. Note the number of sessions currently defined by the nsessions= NN entry. This number is the number of the next available session if more are to be added. It is also the number of sessions currently configured. For example:
  4. Increase the number of sessions defined in the nsessions= NN entry by the total number of sessions to be added. For example, if you are adding four sessions to the default configuration file, the changed entry would read as follows:
  5. Find the [SessionNN] subsection of the configuration file, where NN=(NN-1) (the NN parameter in parentheses being the number of sessions noted in step 3. This should be the last [SessionNN] subsection in the file. It should look similar to the following:
  6. Copy this subsection and change the NN parameter of this newly created subsection to the number noted in step 3. For example:
  7. Add additional subsections as desired such that there are new [SessionNN] subsections for the additional dynamic sessions desired. Increment the NN parameter for each added session. When finished, the NN parameter of the last added subsection should be NN=(NN-1), where the NN parameter in parentheses is the number of total sessions defined in step 4. For example:
  8. In the newly created session subsections, change the port number to the desired port and the application to dynamic. Update the session entry within this subsection to reflect the session number desired for that particular port. For example:
  9. Verify all the other parameters in the newly created subsections to ensure proper settings for the application desired. Refer to the "7318 Configuration File Format" for details on parameters of the [Session] sections.
  10. Use the reboot command from the command shell or power-cycle the 7318 to load the modified configuration file.

Related Information

Configuring a Static Session.

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