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Just like our mailbox analogy, you do
not have to be constantly waiting for a message to receive
your messages. Whenever you are ready, you can retrieve
any messages that have been sent to you and send out any
messages you have been saving up.
Therefore, the first step in creating
a functional MSMQ app is to understand how to create and
work with both queues and messages. If you have not already
done so, you will want to install Ken Rabold's MSMQ control.
This control provides the foundation for the MSMQ Console
to work, and will allow you to see the console in action.
Likewise, you will want to include the MSMQInc.bas
file that he has provided, into any eVB project you create
to handle all of the MSMQ constants. With that in place,
creating a local queue is as simple as this:
' Instantiate the queue information
Set objInfo = CreateObject("CE_MSMQ.MSMQQueueInfo")
' Establish the path to the queue
objInfo.PathName = ".\Private$\PocketPC"
' Create the queue if it does not already
exist
objInfo.Create
You will only be able to create local,
private queues on the Pocket PC, but you may reference both
local and remote queues for sending messages. To create
a message and send it to our new queue, requires only a
few lines as well:
' Open the actual queue
Set objQueue = objInfo.Open(MQ_SEND_ACCESS, _
MQ_DENY_NONE)
' Instantiate the message
Set objMsg = CreateObject("CE_MSMQ.MSMQMessage")
' Configure the message
objMsg.Label = "Test Message"
objMsg.Body = "This is a test message."
' Send the message to the opened queue
objMsg.Send objQueue
' Close the queue
objQueue.Close
Sending a message to a remote queue
follows the same process, but it requires some up-front
configuration. You need to setup a reference to the remote
server in the Pocket PC's host file, since MSMQ does not
support the use of an Internet Protocol (IP) address in
a queue's PathName. You can use Marc
Zimmerman's Pocket Hosts utility, to cross-reference
the server name and IP address in the host's file.
If you want to be fancy about how you
work with messages you can specify such options as a journal,
or a copy of your message that is maintained or sent to
a deadletter queue when non-deliverable. You can also have
acknowledgement messages sent to an administration queue
when key events occur in the life of the message. This all
comes back to accountability for delivery of the message.
As a final piece of insurance, you can
also make the message transactional, which will guarantee
a single delivery of the message to its target. For detailed
information on any of these topics, I would suggest reading
the Ken Rabold's eBook on the subject. It goes into detail
on several of these topics and is a great read for those
interested in developing their own MSMQ apps.
That said, you can add journaling to
your messages like so:
' Send copy to journal queue
' and undeliverable to deadletter queue
objMsg.Journal = MQMSG_JOURNAL Or _
MQMSG_DEADLETTER
Likewise, you can arrange for administrative
notifications this way:
' Instantiate admin queue info
Set objAdmin = objInfo.Open(MQ_SEND_ACCESS, _
MQ_DENY_NONE)
' Request an acknowledgement for the
message
objMsg.Ack = MQMSG_ACKNOWLEDGEMENT_FULL_REACH_QUEUE _
Or MQMSG_ACKNOWLEDGEMENT_FULL_RECEIVE
' Specify the administrative queue
Set objMsg.AdminQueueInfo = objAdmin
These are just additional properties
of a message, with the rest of the process for sending a
message being the same as described earlier. Going back
to the mailbox analogy, these options would be comparable
to the use of registered mail as an acknowledgement, and
a signature request for a transactional message.
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