I started looking into MSMQ very recently so i have basic doubts . If two application needs to communicate lets say server and client I think both will share the same MQ address and when the client update then the Server will be having the MSMQ watcher which will listen to the message pick and use it. So according to me there are three component we need
Client - which knows the Queue location
Queue watcher - which watches the queue
service -- to which queue watcher will send the message to
Tom Hollander wrote an excellent series of three articles on WCF and MSMQ. They helped me alot when I had to build an application to communicate via MSMQ. There is a third article but Stack Overflow won't let me post since I'm a new user. You can find the link to it from the 2nd article.
MSMQ, WCF and IIS: Getting them to play nice (Part 1)
MSMQ, WCF and IIS: Getting them to play nice (Part 2)