Channel Model Overview in WCF

Introductions 

WCF endpoints are the main components, those communicate withe the external world, And this communication was done b using\g a communication stack called channel stack.



Here in this article we will go through the little basics of channel stacks in WCF service programing.

Behind The Scene 

See the image below, which shows a basic diagram of the channel stack and the HTTP stack.

In wcf services when two stacks communicates, then the corresponding layers communicates between them. That is the HTTP layer communicates with the HTTP layer of the other stack and respectively.

Channel Stack

Now, the differences: While the TCP stack was designed to provide an
abstraction of the physical network, the channel stack is designed to
provide an abstraction of not only how the message is delivered, that
is, the transport, but also other features such as what is in the
message or what protocol is used for communication, including the
transport but much more than that. For example, reliable session binding
element is part of the channel stack but is not below the transport or
the transport itself.



Messages flow through the communication stack as Message
objects. As shown in figure above, the bottom channel is called a
transport channel. It is the channel that is responsible for sending and
receiving messages to and from other parties.

Each channel implements one or more interfaces known as channel shape
interfaces or channel shapes. Those channel shapes provide the
communication-oriented methods such as send and receive or request and
reply that the channel implements and the user of the channel calls.

The interface is call IChannel, The five channel shapes that extend IChannel are:

• 
  IInputChannel
  
  
  
  


• 
  IOutputChannel
  
  
  
  


• 
  IRequestChannel
  
  
  
  


• 
  IReplyChannel
  
  
  
  


• 
  IDuplexChannel
  

The channel shapes are patterned after some of the fundamental message
exchange patterns supported by existing transport protocols. For
example, one-way messaging corresponds to an IInputChannel/IOutputChannel pair, request-reply corresponds to IRequestChannel/IReplyChannel pairs and two-way duplex communications corresponds to IDuplexChannel

Hope, this article gives you some basic idea about channel stacks in WCF.

Happy Coding...




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