WebSphere MQ products allow you to write your own message channel agent
(MCA) programs or to install one from an independent software vendor.
You might want to do this to make a WebSphere MQ product interoperate over
your own, proprietary communications protocol or to send messages over a
protocol that WebSphere MQ does not support. (You cannot write your own
MCA to interoperate with a WebSphere MQ-supplied MCA at the other end.)
If you decide to use an MCA that was not supplied by WebSphere MQ, you need
to consider the following.
- Message sending and receiving
- You need to write a sending application that gets messages from wherever
your application puts them, for example from a transmission queue (see the
WebSphere MQ Application Programming Reference book),
and sends them out on a protocol with which you want to communicate.
You also need to write a receiving application that takes messages from this
protocol and puts them onto destination queues. The sending and
receiving applications use the message queue interface (MQI) calls, not any
special interfaces.
You need to ensure that messages are delivered once and once only.
Syncpoint coordination can be used to help with this.
- Channel control function
- You need to provide your own administration functions to control
channels. You cannot use WebSphere MQ channel administration functions
either for configuring (for example, the DEFINE CHANNEL command) or monitoring
(for example, DISPLAY CHSTATUS) your channels.
- Initialization file
- You need to provide your own initialization file, if you require
one.
- Application data conversion
- You will probably want to allow for data conversion for messages you send
to a different system. If so, use the MQGMO_CONVERT option on the MQGET
call when retrieving messages from wherever your application puts them, for
example the transmission queue.
- User exits
- Consider whether you need user exits. If so, you can use the same
interface definitions that WebSphere MQ uses.
- Triggering
- If your application puts messages to a transmission queue, you can set up
the transmission queue attributes so that your sending MCA is triggered when
messages arrive on the queue.
- Channel initiator
- You may need to provide your own channel initiator.
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