HP 3000 Manuals HP 3000 Manuals
Reverse Virtual Terminal
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
NS3000 connections (either NS3000/V or NS3000/XL). 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.