How terminal emulation works in Anzio

Introduction

The Anzio family of products are terminal emulation packages that work over either a serial or network connection, to provide standard terminal emulation from a PC to a host system.

Anzio startup

Over a serial connection, Anzio must be set to match what your host default is (refer to your host documentation on setting up a TTY). Over a network connection, Anzio handles telnet negotiation options, where it can tell the host what terminal type it is. Anzio products support many terminal emulations and reports their term name to the host system. You can explicitly set a different term name if you need to, through the Communicate : TERM Name option. An example of why you may need to do this is that the early releases of Linux host operating system did not have support for a terminal type of vt220, but did support vt320 (identical terminals), so the TERM name can be set to vt320 and the host thinks the emulation Anzio is running is vt320.

Also associated with a terminal type and loaded on startup is a keys file (a file with an extension of .kys). This file contains the mappings for the current terminal type, as well as any user-defined mappings and macro keys. See our document on Remapping Keyboards With Anzio for more information on the keys file.

(default key file for each terminal type is in blue)

* The Anzio terminal type is a special terminal emulation. It is derived from the VT220, but contains color and special key support not normally found.

** The SCO ANSI terminal type also covers standard ANSI terminal emulation. By default the SCO OpenServer 5.0.6 version is supported. If you experience color or emulation problems, you can change this for pre-5.0.6 support in the Advanced Options dialog.

Debugging terminal emulation problems

There are many factors that go in to the behavior of a particular terminal. This includes the terminal definition on the host, the host application's behavior, the PC's keymapping, the type of connection, and more.

Many UNIX hosts use either TERMCAP or TERMINFO for defining their terminal types. Other hosts, such as VAX, Windows NT, and others, have their own definition of what constitutes a terminal. In general, all hosts have a set of definitions that tell the operating system what to send to display characters, to position the cursor, to change attributes (such as blink, underline, bright), and in general how to behave to keyboard responses from these terminals.

On UNIX, you can see your current terminal settings by doing the following at a shell prompt

stty -a

This lists all "stty" (terminal) settings that are current for your terminal type. You need to refer to a book on TERMCAP or TERMINFO for more information on what each of these do. With the "stty" command you can also change these settings on the fly to match what you would like. You can also do an INFOCMP on many hosts to display all default settings for a terminal type, i.e.

infocmp vt220

(again refer to documentation describing the results). It is important to know the capabilities of your host for a specific terminal type. As an example, while a standard vt220 supports passthrough (transparent) printing, many older hosts TERMCAP and TERMINFO files do not describe the two critical elements needed for it to work, the MC4 and MC5 sequences.

Check with your host as to the capabilities it includes when you run in to problems with the emulation's behavior.

Like the host end, many applications on the host are also programmed for a specific terminal type in order to take advantage of screen positioning, passthrough printing, screen clear and scrolling, and other terminal-specific options.

Within the Communicate menu in Anzio, you can control the terminal type and the terminal TERM name sent to the host. When the TERM name is blank, the default (from the above tables) is sent to the host when asked for by the host. Also under the File menu is the "keys" file being read. The proper key file must be loaded for the appropriate terminal type to work correctly.

Note : If you change terminal types, be sure to re-read the proper .kys file using the File : Read Keys menu item. This is automatic in version 12.0 or later, but not in prior releases.