tn3270(1) CLIX tn3270(1)
NAME
tn3270 - Permits full-screen login to remote IBM systems
SYNOPSIS
tn3270 [-nfilename] [-tcommandname] [sysname [port]]
FLAGS
[-nfilename]
Specifies a file to receive network trace data output (from
commands toggle netdata and toggle options, see telnet(1); the
default is for output to be directed to the standard error file.
[-tcommandname]
Specifies a CLIX command to process IBM 4994 style transparent mode
data received from the remote IBM machine.
[sysname]
Specifies the name of the remote system. If the remote name is not
specified, the user will be prompted for a command (see following).
[port] Specifies the port to connect to on the remote system. Normally,
tn3270 attempts to connect to the standard TELNET port (port 23) on
the remote machine.
DESCRIPTION
The tn3270 command permits full-screen, full-duplex connection from a CLIX
machine to an IBM (or compatible) machine. The tn3270 utility gives the
appearance of being logged in to the remote machine from an IBM 3270
terminal. You must have an account on the remote machine to log in. The
tn3270 utility looks to the user like the Yale ASCII Terminal
Communication System II. The tn3270 command is actually a modification of
the Arpanet TELNET user interface (see telnet(1)) that will, in certain
circumstances, interpret and generate raw 3270 control streams.
When tn3270 first connects to the remote system, it will negotiate to go
into 3270 mode. Part of this negotiation involves telling the remote
system what model 3270 it is emulating. In all cases, tn3270 emulates a
3278 terminal. To decide which specific model, tn3270 looks at the number
of lines and columns on the actual terminal defined in the TERM
environment variable; see terminfo(4). The terminal (or window in which
tn3270 is running, on multiple window systems) must have at least 80
columns and 24 lines, or tn3270 will not go into emulation mode. If the
terminal does have at least 80 columns and at least 24 lines, one of the
following emulations takes place:
Minimum Size Emulated
Rows Columns Terminal
2/94 - Intergraph Corporation 1
tn3270(1) CLIX tn3270(1)
____ _______ ____________
27 132 3278 Model 5
43 80 3278 Model 4
32 80 3278 Model 3
24 80 3278 Model 2
Emulation of the 3270 terminal is done in the CLIX process. This
emulation involves mapping 3270-style commands from the host into
appropriate sequences to control the user's terminal screen.
The tn3270 command uses curses(3) and the /usr/lib/terminfo directory to
do this. The emulation also involves simulating the special 3270 keyboard
keys (program function keys, etc.) by mapping sequences of keystrokes from
the ASCII keyboard into appropriate 3270 control strings. This mapping is
terminal dependent and is specified in a description file, /etc/map3270,
(see map3270(4)) or in an environment variable MAP3270 (and, if necessary,
MAP3270A, MAP3270B, and so on - see mset(1). Any special function keys on
the ASCII keyboard are used whenever possible. If an entry for the user's
terminal is not found, tn3270 looks for an entry for the terminal type
unknown. If this not found, tn3270 uses a default keyboard mapping file
located at /usr/ip32/tn3270/tn3270/ascii/default.map.
The first character of each special keyboard mapping sequence is either an
ASCII escape (ESC), a control character, or an ASCII delete (DEL). If the
user types an unrecognized function key sequence, tn3270 sends an ASCII
bell or a visual bell if defined in the user's terminfo entry, to the
user's terminal and nothing is sent to the IBM host.
If tn3270 is invoked without specifying a remote host system name, it
enters local command mode, indicated by the prompt tn3270>. In this mode,
tn3270 accepts and executes all the commands of telnet, plus the following
additional command:
transcom
The transcom command specifies a CLIX command for IBM 4994 style
transparent mode processing.
The tn3270 command mode may also be entered, after connecting to a host,
by typing a special escape sequence. If tn3270 has succeeded in
negotiating 3270 mode with the remote host, the escape sequence will be as
defined by the map3270 (see map3270(4)) entry for the user's terminal type
(typically the <Ctrl-C> sequence); otherwise the escape sequence will
initially be set to the single character '^]', or <Ctrl-]>.
While in command mode, any host login session is still alive, but
temporarily suspended. The host login session may be resumed by entering
an empty line (press the RETURN key) in response to the command prompt. A
session may be terminated by logging off the foreign host, or by typing
quit or close while in local command mode.
2 Intergraph Corporation - 2/94
tn3270(1) CLIX tn3270(1)
FILES
/usr/lib/terminfo
/etc/map3270
NOTES
The IBM 4994 style transparent mode command is invoked when tn3270
receives IBM 4994 style transparent output from the remote host. Output
and input pipes are created for communication between the two processes.
The pipes are closed when a 3270 clear command is received from the remote
hosts, signalling the end of transparent mode output. Transparent mode is
necessary for sending ASCII control characters over the 3270 terminal
connection; ASCII graphics terminal support is accomplished this way.
Developers of transcom commands should note that the transcom stdin pipe
end will be in CBREAK mode, with ECHO and CRMOD turned off.
RELATED INFORMATION
Commands: mset(1), telnet(1)
Functions: curses(3)
Files: terminfo(4), map3270(4)
Yale ASCII Terminal Communication System II Program Description/Operator's
Manual (IBM SB30-1911)
2/94 - Intergraph Corporation 3