6100 ADCCP Programming Manual

Clearing the X.21 Connection
Writing Applications that Use ADCCP/X21
5–6 069225 Tandem Computers Incorporated
Clearing the X.21
Connection
Your application can clear the X.21 connection at any time during the call
establishment or connection phases by issuing a WRITEREAD call with an
(83) DISCONNECT request. If your application has requested ADCCP/X21 to wait for
charging information from the DCE, it must provide enough space for this information
in the (83) DISCONNECT response buffer. ADCCP/X21 delivers a maximum of 20
bytes of charging information to your application if the application requests it.
The (83)DISCONNECT request is described in detail in Section 6, “Requests and
Responses.”
Closing the Line After an application has finished using a the line, it should issue a CLOSE call
corresponding to every one of its OPEN call. Because a line is limited to 15 concurrent
OPEN calls, an application should close any opens that it does not need.
Error Recovery You use the same error trapping and recovery strategy on an ADCCP/X21 line as you
use on a 6100 ADCCP line. ADCCP/X21 delivers a Status code in all response
messages. The Status code indicates whether or not your request finished successfully.
Response codes that refer to features of the X.21 network are described under “Status
Code Definitions” in Section 6, “Requests and Responses.” Section 4, “Writing
Applications That Use ADCCP,” describes an error recovery strategy for your
application.