Using Telnet 3270 terminal emulators

You can use third-party TN3270 terminal emulators as CICS clients. The TN3270 emulator session can run on the same machine as Enterprise Server or on a network machine.

To use a TN3270 terminal emulator, you need to create a TN3270 listener in Enterprise Server Administration.

When you specify the Endpoint for the listener, we recommend that you use any port number above 5000 that isn't in use, since the usual port number for Telnet, 23, might already be in use for non-3270 Telnet access.

The TN3270 emulator session can run on the same machine as Enterprise Server or on a remote machine.

By default MSS installs TN3270 terminals dynamically as basic 3270 terminals. This means that some of the more advanced features of your TN3270 terminal emulator won't be available. To make these features available, you need to enable MSS to associate the TN3270 device type and a CICS typeterm definition, known as a T-Type in ESMAC.

The TN3270 device type is specified by the emulator software and might or might not be configurable. Device types indicate the ability of the emulator to support various elements of the 3270 data stream, for example, color, extended attributes, the use of a TCTUA etc.

During the connection negotiation the TN3270 client sends a data packet indicating which device it wishes to emulate. MSS uses this data to identify a T-Type entry which defines this terminal type.

To make this work you need to:

Define a T-Type entry that matches the capabilities of the TN3270 terminal emulator.

Define a terminal model entry on the ESMAC Term page which points to this typeterm definition. Required fields for the terminal model entry are:

Name	Unique name of this terminal model
Model	O(nly), Y(es) , or N(o)
Model name	The TN3270 device type
Terminal type	The name of the T-type entry to use with this terminal

For example, suppose the TN3270 client software is configured to emulate an IBM 3279 MOD2 with support for extended attributes. At connection time MSS searches for a terminal model entry with the name TN32792E. The terminal type specified in this terminal entry is then used to look up the terminal's details in the T-type entry .

Configuring screen size

If you want to use a screen size other than the default, which is MOD2 (24 x 80), you need to set the environment variable ES_TN3270_FORCE_ALT=ON before starting the enterprise server. You can then change the size to MOD1 (12 x 80), MOD2 (24 x 80), MOD3 (32 x 80), MOD4 (43 x 80), and MOD5 (27 x 132) during the terminal session.

Note: Micro Focus terminal handling does not support dynamic window sizing. If you switch from a larger terminal to a smaller one, then the window size will remain at the larger window's dimensions.

To use custom dimensions, you need to set ES_TN3270_FORCE_ALT=ON and also specify the screen size in the Alt. Screen Width and Alt. Screen Height fields of the ESMAC T-Type page.