AT&T UNIX™PC Unix System V Users Manual - tenox

LAYERS (5) LAYERS (5)
NAME
layers - protocol used between host and windowing terminal under
layers(!)
SYNOPSIS
#include
DESCRIPTION
layers are asynchronous windows supported by the operating system in a
windowing terminal. Communication between the UNIX system
processes and terminal processes under layers(l) occurs via multiplexed
channels managed by the respective operating systems using a protocol
as specified in xtproto(5).
The contents of packets transferring data between a UNIX system process
and a layer are asymmetric. Data sent from the UNIX system to a particular
terminal process is undifferentiated and it is up to the terminal process
to interpret the contents of packets.
Control information for terminal processes is sent via channel 0. Process
0 in the windowing terminal performs the designated functions on behalf
of the process connected to the designated channel. These packets take
the form:
command, channel
except for timeout and jagent information which take the form
command, data . ..
The commands are the bottom eight bits extracted from the following
ioctl(2) codes:
JBOOT Prepare to load a new terminal program into the designated
layer.
JTERM Kill the downloaded layer program, and restore the default
window program.
JTIMO Set the timeout parameters for the protocol. The data consist
of two bytes: the value of the receive timeout in seconds,
and the value of the transmit timeout in seconds.
JTIMOM Set the timeout parameters for the protocol. The data consist
of four bytes in two groups: the value of the receive timeout
in milliseconds (the low eight bits followed by the high eight
bits) and the value of the transmit timeout (in the same format).
JZOMBOOT
Like JBOOT, but do not execute the program after loading.
JAGENT Send a source byte string to the terminal agent routine and
wait for a reply byte string to be returned.
The data are from a bagent structure (see jagent(5)) and consist
of a one-byte size field followed by a two-byte agent
command code and parameters. Two-byte integers transmitted
as part of an agent command are sent with the high-order
byte first. The response from the terminal is generally
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