Creating Services with the WCF - Channels (Page 2 of 4 )
Channels facilitate communication between clients and services in WCF. The ServiceHost creates a channel listener for each endpoint, which generates a communication channel. The proxy creates a channel factory, which generates a communication channel for the client. Both communication channels must be compatible for messages between them to be processed effectively. In fact, the communication channel is comprised of a layered channel stack--each channel in the stack is responsible for performing a particular activity while processing a message. The channel stack includes a transport channel, a message-encoding channel, and any number of message processing channels for security, reliability, and other features. Without getting into specifics, the binding controls which channels participate in the channel stack, as shown in Figure 1-16. (The details of channels and bindings are explored in Chapter 3.)
Figure 1-16. Messages are processed by equivalent channels at the client and service
Behaviors
Behaviors also influence how messages are processed by the service model. While services and endpoints determine the core communication requirements and metadata shared with clients, a behavior modifies the way messages are processed as they flow through the channel stack. Behaviors are local to the client or service--thus, they are not included in metadata.
There are behaviors to control many service model features such as exposing metadata, authentication and authorization, transactions, message throttling, and more. Behaviors are enabled either in configuration or by applying behavior attributes to client proxies and services.
In this chapter, you'll learn how to apply the metadata behavior to a service, but other behaviors will be explored throughout this book as they relate to each feature.
Next: Creating a New Service from Scratch >>
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 This article is excerpted from chapter 1 of the book Learning WCF A Hands-on Guide, written by Michele Leroux Bustamante (O'Reilly, 2007; ISBN: 0596101627). Check it out today at your favorite bookstore. Buy this book now.
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