Message Queuing provides a way for applications to communicate asynchronously, and has often been compared to e-mail, but for applications rather than people. On Windows, Message Queuing is implemented in Microsoft Message Queuing, or MSMQ. A client application can communicate with a server by sending data in the form of an MSMQ message to a particular queue, where the server application can retrieve it and process it. Because the message will remain on the queue until it is retrieved, we can guarantee that it will be processed at some point, even if the server application is down when the message is sent.

In this book, we look at how we can use MSMQ to provide robust, asynchronous communication between our applications. MSMQ provides three APIs that we can use to incorporate message queuing into our applications - a C API that we can use from unmanaged C/C++ code, a COM component that we can use from VB or C++ code, and the System.Messaging namespace, which provides a simple way to integrate MSMQ with managed C# or VB.NET applications. This will be the only book that covers all these APIs.