The Reverse Virtual Terminal (Reverse VT) service allows an
application program to receive information from and send information
to terminals located on other systems. All the systems involved
must be connected via NS 3000 connections (either NS 3000/V
or NS 3000/iX). The Reverse VT service must be initiated
from the system on which the application resides.
Two important points for Reverse VT are as follows:
Reverse VT is supported for terminal
type 10 only;
The terminal must be available
in order to be opened successfully by the application. That is,
no one can be logged on and no other application can be accessing
the terminal. Pressing [Return], for example, will
make a terminal unavailable (the system is waiting for a logon attempt)
until the logon timer expires.
To gain access to a remote terminal via Reverse VT, you can
specify the VTERM option in the
FILE command, which designates the terminal as
a remote device. Or the application program itself may include the
VTERM option in the device
parameter of the FOPEN intrinsic
which opens the connection to the device. (For the syntax of the
FILE command and the FOPEN
intrinsic, when used to access remote files and devices, see the
Remote File Access chapter of this manual.)
The format for the file equation is either:
FILE X=X:envID;DEV=#ldev;VTERM **8-character environment ID** |
or
FILE X=X;DEV=envID#ldev;VTERM **8-character environment ID** |
The format for the FOPEN
device parameter is:
#ldev;VTERM [Return] **must be terminated by ASCII value
for carriage return** |
In the FOPEN call, the location
of the device may be specified either in the formaldesignator
parameter (X:envID)
or in the device parameter (envID#ldev;VTERM
[Return]). If the FOPEN
call indicates the location of the file, you can specify the VTERM
option in a file equation issued directly on the remote terminal's
node:
ENV1#FILE X;DEV=# ldev;VTERM |
The ldev parameter is either the
device class name or the logical device number of the remote terminal.
If you specify a device class name rather than the logical device
number of a terminal, the first available terminal in the device
class table will be used.
Because the VTERM option
is specified, the application program communicates with the remote
terminal by way of the Virtual Terminal rather than by way of Remote
File Access. In both VT and RFA, the remote terminals function as
non-session I/O devices. With RFA, you have to create a remote session
on the node where the terminal resides. With Reverse Virtual Terminal,
however, the application program does not establish a remote session
on the node where the terminal resides. The terminal users cannot
call subsystems or issue commands to the remote system. A privileged
mode program can communicate with the terminal in nowait mode by
setting bit 4 in the FOPEN aoption
parameter. The application program will not recognize a [BREAK]
or [CTRL]-Y issued from the remote terminal's
side of the connection.
