I want to accomplish this:
A dual directional point-2-point setup:

1. client_1 writes message to a InQueue
and saves the messageid.

2. client_2 reads new messages from Inqueue,
processes them and writes them to a OutQueue,
with the _same_ messageId as it previously got.

3. client_1 waits for a message on the OutQueue
with the same messageId it saved.

In step 3 I want to make sure that client_1 reads
the right response back. I can do this by creating
a message selector:

QueueReceiver queueReceiver =
session.createReceiver(ioQueue,
"JMSMessageId = 'long hex string'");

However, it seems like the message ID itself isn't in
the JMS message, but in the IBMs MQ header, so I can't
use it in the message selector.

I know this by browsing the queue after step 1;
the JMS message only contains my data and any user-defined
headers but the message Id is somehow wrapped into the IBM MQ.

How can I select from the messages based on the message id?

I have only one option: to have client_1 get a unique number every
time and put that in the JMS-header and make sure that
client_2 puts it back there. This adds some complexity though.

Any tips? I know I can do a QueueRequestor, then I know
the right client gets the right response, but would like
to take the above approach, because I want client_2 to be able to
not acknowledge the message if it encounters errors.

/Thomas