The Echo sample programs echo a message from a message queue to the reply queue. See Features demonstrated in the sample programs for the names of these programs.
The programs are intended to run as triggered programs.
On OS/400, OS/2, UNIX systems, and Windows systems, their only input is an MQTMC2 (trigger message) structure that contains the name of a target queue and the queue manager. The COBOL version uses the default queue manager.
On OS/400, for the triggering process to work, you must ensure that the Echo sample program you want to use is triggered by messages arriving on queue SYSTEM.SAMPLE.ECHO. To do this, specify the name of the Echo sample program you want to use in the ApplId field of the process definition SYSTEM.SAMPLE.ECHOPROCESS. (For this, you can use the CHGMQMPRC command, described in WebSphere MQ for iSeries V5.3 System Administration.) The sample queue has a trigger type of FIRST, so, if there are already messages on the queue before you run the Request sample, the Echo sample is not triggered by the messages you send.
When you have set the definition correctly, first start AMQSERV4 in one job, then start AMQSREQ4 in another. You could use AMQSTRG4 instead of AMQSERV4, but potential job submission delays could make it less easy to follow what is happening.
Use the Request sample programs to send messages to queue SYSTEM.SAMPLE.ECHO. The Echo sample programs send a reply message containing the data in the request message to the reply-to queue specified in the request message.
The program opens the queue named in the trigger message structure it was passed when it started. (For clarity, we will call this the request queue.) The program uses the MQOPEN call to open this queue for shared input.
The program uses the MQGET call to remove messages from this queue. This call uses the MQGMO_ACCEPT_TRUNCATED_MSG, MQGMO_CONVERT, and MQGMO_WAIT options, with a wait interval of 5 seconds. The program tests the descriptor of each message to see if it is a request message; if it is not, the program discards the message and displays a warning message.
For each line of input, the program then reads the text into a buffer and uses the MQPUT1 call to put a request message, containing the text of that line, on to the reply-to queue.
If the MQGET call fails, the program puts a report message on the reply-to queue, setting the Feedback field of the message descriptor to the reason code returned by the MQGET.
When there are no messages remaining on the request queue, the program closes that queue and disconnects from the queue manager.
On OS/400, the program can also respond to messages sent to the queue from platforms other than WebSphere MQ for iSeries, although no sample is supplied for this situation. To make the ECHO program work, you:
The ECHO program requests the queue manager to perform message data conversion, if this is needed.