6100 ADCCP Programming Manual

Performing ADCCP Tasks
Writing Applications that Use ADCCP/X21
069225 Tandem Computers Incorporated 5–5
If your application issues an active (83) DISCONNECT request while the leased
line is in the connected state, ADCCP/X21 releases the connection.
If a leased-line connection has been released by an (83) DISCONNECT request,
ADCCP/X21 will attempt to establish a new connection upon receiving either an
(82) CONNECT request or a (6) START OPERATION request.
If a leased line connection has been released by a (7) STOP OPERATION request,
ADCCP/X21 will attempt to establish a new connection only upon receiving of a
(6)START OPERATION request.
Preparing for
Unexpected
Disconnects
During the connected phase of the X.21 link, your application should always have a
pending request to monitor DCE disconnects. Use the passive form of the (83)
DISCONNECT request in your application for this purpose.
Although ADCCP/X21 always monitors the communications line for clearing by the
network, an outstanding passive (83) DISCONNECT request ensures that your
application is notified immediately by ADCCP/X21 if the line is cleared.
The (83) DISCONNECT request is described in detail in Section 6, “Requests and
Responses.”
Performing ADCCP
Tasks
Once the X.21 link is established, your application can set up the ADCCP protocol and
exchange data with remote stations. To do this, your application needs to perform the
following tasks:
Define a station list if you want a multipoint ADCCP link on the X.21 connection.
To do this, your application issues a WRITEREAD call with a (69) DEFINELIST
request.
Establish ADCCP protocol relationships by setting the mode of each station. Your
application issues one or more (67) MODE SET requests to account for each station
on the station list.
To send data, make a WRITEREAD call with the (65) SENDTEXT request.
To receive data, make a WRITEREAD call with the (66) RECEIVETEXT request.
To shut down the ADCCP link, put the station in DISC mode by issuing a
WRITEREAD with a (67) MODE SET request.
These application tasks are the same for ADCCP/X21 as for 6100 ADCCP. See
Section 4 , “Writing Applications That Use ADCCP,” for a discussion of the tasks and
the requests that you use in your application to set up an ADCCP link and transfer
frames.