Pathway/iTS TCP and Terminal Programming Guide

Processing Unsolicited Messages

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Detecting the Arrival of Unsolicited Messages

Each requester program has its own unsolicited-message queue. In addition, each

requester program has its own copy of the PW-UNSOLICITED-MESSAGE-QUEUED

special register that is global to any program units called by that requester.

When the TCP receives an unsolicited message addressed to one of its requesters, it

places the message in the appropriate queue and sets the value of the associated

PW-UNSOLICITED-MESSAGE- QUEUED register to YES.

A requester can detect the arrival of an unsolicited message in any of the following

ways:

•

By testing the content of its PW-UNSOLICITED-MESSAGE-QUEUED special

YES signifies that one or more messages have arrived and are waiting to be

processed; NO signifies that the queue is empty.

•

By performing a RECEIVE UNSOLICITED MESSAGE statement as a waited input

operation

•

By including an ESCAPE ON UNSOLICITED MESSAGE clause in ACCEPT or

SEND MESSAGE statements

Accepting Unsolicited Messages

Requesters obtain the text of an unsolicited message by performing a RECEIVE

UNSOLICITED MESSAGE statement. Messages can move either directly into

working-storage or move indirectly there from a Message Section templates.

Replying to Unsolicited Messages

When a requester has constructed an appropriate response message, it replies to an

unsolicited message by performing a REPLY TO UNSOLICITED MESSAGE

statement. After replying to the message, the requester is then free to accept and process

another unsolicited message.

Having received one message (by performing a RECEIVE UNSOLICITED MESSAGE

statement), the requester cannot perform another RECEIVE UNSOLICITED

MESSAGE statement until it has replied to the first message (by using a REPLY TO

UNSOLICITED MESSAGE statement).