55.2. Message Service Technology Explained

This section explains the basic workings of the Message Service in preparation for learning how to use the client- and server-side features to build real messaging applications. Figure 55-1 shows the main components of such an application.

55.2.1. Publish and Subscribe

Flex and AIR clients can both interact with the Flex Message Service, first by publishing (or sending) messages to a Message Service destination and second by subscribing to one or more destinations, in order to receive the messages that are sent to them. This is an implementation of the publish-subscribe paradigm, which is an asynchronous method of communication that decouples the senders from the receivers of messages, so one can know nothing of the other. A sender can publish a message without knowledge of whether it will be consumed by any client, and similarly, a receiver can subscribe and consume messages with no knowledge of where they originated.