Overview

MSMQ is a message queuing service. Message queuing is not the same as mail messaging a service with which it is often confused. Whereas mail messaging (or just "messaging") is used by people to send mail messages to other people and communication is directly between people, message queuing is a service used to enable messages to be sent between processes. Thus, a client process could send a message, with data in it about an order, to a server process for that process to act on the order.

Message queuing products and services can support asynchronous processing of communicating processes. The sending process hands the message to the message-queuing service and can then carry on working; it doesn't have to wait for a reply. In order to achieve this, the products use a store and forward-like approach to handle interprocess communication at runtime. When one process sends another process or processes a message, the middleware stores the message on queues along the route the message takes.

Processes which use message queuing services are actually acting in a peer-to-peer way process A can send process B a message and in turn, process B can also send process A a message.

Figure 14.1: MSMQ

Figure 14.2: Store and forward queuing

Message Passing vs. Message Queuing

You may have heard the terms message queuing and message passing. A message passing service or product enables one process to send another process a message by addressing the message directly to the receiving process SEND MESSAGE nnnn...