SNAX/HLS Application Programming Manual

SCOBOLX Applications
SNAX/HLS Programming Standards
104707 Tandem Computers Incorporated 1–9
When an unsolicited message arrives and your SEND MESSAGE statement includes
the ESCAPE ON UNSOLICITED MESSAGE clause, or when a timeout occurs because
your SEND MESSAGE statement includes the TIMEOUT clause, Pathway’s TCP
responds by sending an interrupt signal (CONTROL-26) to SNAX/HLS. In response,
SNAX/HLS completes the original verb that you specified in the SEND MESSAGE
text in one of three ways:
Normally There is a brief timing window where SNAX/HLS has already
completed the verb but your TCP did not yet notice it. In this case,
your SEND MESSAGE statement completes as if the interrupt cause
had not occurred.
No Data If your SEND MESSAGE sent a SNAX/HLS RECEIVE-DATA or a
RECEIVE-CONTROL-WAIT verb, SNAX/HLS simply cancels your
verb by returning a reply code of 187. The session acts as if the verb
had never been issued. This condition also applies to a SEND-AND-
RECEIVE-DATA verb that has been turned into a RECEIVE-DATA
verb after the send portion is complete. Any data that arrives is
queued on your session and can be retrieved by subsequent
RECEIVE-DATA verbs. As a result, there is no loss of data.
Forthcoming If your SEND MESSAGE sent a SNAX/HLS verb that requires long-
term activity (and was not a RECEIVE-DATA or
RECEIVE-CONTROL-WAIT verb as described above), the work that
was started on behalf of the verb is not interrupted. Your original
verb is completed with a reply code of 189. After treating the cause
of the interrupt, you should use a RECEIVE-DATA verb to wait for
the completion of the original work, as well as to retrieve any data
that might have been queued to your session in the interim. No data
is lost during this interaction.
Pathway’s TCP presents these various completions to your program as one of the
following three events:
Normal Your SEND MESSAGE completes with
TERMINATION-STATUS pointing to one of your CODE
clauses.
Unsolicited Message Your SEND MESSAGE completes with
TERMINATION-STATUS pointing to your ESCAPE ON
UNSOLICITED MESSAGE clause.
Error Your SEND MESSAGE completes by executing the ON ERROR
statement (or aborting your program). The
TERMINATION-STATUS and TERMINATION-SUBSTATUS
reveal the cause.