Channels and channel sets
A Flex component uses a channel to communicate with a BlazeDS server. A channel set contains channels; its primary function is to provide connectivity between the Flex client and the BlazeDS server. A channel set contains channels ordered by preference. The Flex component tries to connect to the first channel in the channel set and in the case where a connection cannot be established falls back to the next channel in the list. The Flex component continues to go through the list of channels in the order in which they are specified until a connection can be established over one of the channels or the list of channels is exhausted.
Flex clients can use different channel types such as the AMFChannel and HTTPChannel. Channel selection depends on a number of factors, including the type of application you are building. If non-binary data transfer is required, you would use the HTTPChannel, which uses a non-binary format called AMFX (AMF in XML).

Messages
All messages have client-side (ActionScript) implementations and server-side (Java) implementations because the messages are serialized and deserialized on both the client and the server.

Endpoint
 It is important that the channel and the endpoint use the same message format.

MessageBroker
The MessageBroker is responsible for routing messages to services and is at the core of BlazeDS on the server. After an endpoint initially processes the request, it extracts the message from the request and passes it to the MessageBroker. The MessageBroker inspects the message's destination and passes the message to its intended service. If the destination is protected by a security constraint, the MessageBroker runs the authentication and authorization checks before passing the message along

Services and destinations
Services and destinations are the next links in the message processing chain in the BlazeDS server. The system includes four services and their corresponding destinationsBlazeDS:
•     RemotingService and RemotingDestination
•     HTPProxyService and HTTPProxyDestination
•     MessageService and MessageDestination
Services are the targets of messages from client-side Flex components. Think of destinations as instances of a service configured in a certain way. For example, a RemoteObject component is used on the Flex client to communicate with the RemotingService. In the RemoteObject component, you must specify a destination  id  property that refers to a remoting destination with certain properties, such as the class you want to invoke methods on. The mapping between client-side Flex components and BlazeDS services is as follows:
•     HTTPService and WebService communicate with HTTPProxyService/HTTPProxyDestination         (RPC services)
•     RemoteObject communicates with RemotingService/RemotingDestination    (RPC services)
•     Producer and Consumer communicate with MessageService/MessageDestination   (Message services)

Adapters and assemblers
Although the BlazeDS server comes with a rich set of adapters and assemblers to communicate with different systems, custom adapters and assemblers can be plugged into the BlazeDS server. Similarly, you do not have to create all destinations in configuration files, but instead you can create them dynamically at server startup or when the server is running.

Configuration tokens
The configuration files sometimes contain special  {server.name}  and  {server.port}  tokens. These tokens are replaced with server name and port values based on the URL from which the SWF file is served when it is accessed through a web browser from a web server. Similarly, a special  {context.root}  token is replaced with the actual context root of a web application.
Note: If you use server tokens in a configuration file for an Adobe AIR application and you compile using that file, the application will not be able to connect to the server. You can avoid this issue by configuring channels in ActionScript rather than in a configuration file.

How you define JVM options depends on the application server you use. For example, in Apache Tomcat, you can define an environment variable JAVA_OPTS that contains tokens and their values, as this code snippet shows:
JAVA_OPTS=-Dmessaging.channel=my-amf -Dmy.token=myValue