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WCF Service Binding Explained

This article offers a brief explanation on the basic concepts of the Communication part in the Windows Communication Foundation - WCF. To further illustrate the concepts, the article provides examples of configuration settings in the service's web.config file and the client code.
 
In order to communicate with a WCF service, the client needs to know simple details like ABC of the service.
 

The ABC of Windows Communication Foundation!!!

 
Before we learn the ABC of WCF, we need to know how a WCF service is made accessible to the clients.
 
A WCF service allows communication through an Endpoint. And the endpoint is the only point of communication of the WCF service that enables message exchange with the client as shown in Figure 1.
 
Figure1.gif 
Figure 1
 
And this Endpoint needs to set the ABC attributes of the WCF service as shown in Figure 2.
 
Figure2.gif 
Figure 2
 
Thus in the WCF world, ABC is an abbreviation of Address, Binding and Contract attributes of an Endpoint. 
 

An example of the Endpoint

 
Let us quickly run through an example of an endpoint setting in the web.config file at the service side. 
  1. <!-- Endpoint settings in WCF service -->  
  2. <endpoint address="http://localhost:8731/EmployeeWCFService.ServiceImplementation.Manager/"   
  3. binding="basicHttpBinding"   
  4. contract="EmployeeWCFService.ServiceContract.IEmployee" />  
Where, address is the network address of the service, binding specifies transport protocol (HTTP, TCP, etc.) selected for the service and contract is the interface the service implements.
 
For the purpose of this article, we are going to emphasize on the Binding part of the WCF communication mechanism.
 

So, what is the Binding?

 
The Binding is an attribute of an endpoint and it lets you configure transport protocol, encoding and security requirements as shown in Figure 3
 
Figure3.gif 
Figure 3
 

Types of Binding

 
One of the design goals of WCF is to unify the way distributed systems are developed prior to release of .Net Framework 3.0. WCF offers a single development framework for all scenarios where distributed solutions were implemented using different technologies such as ASMX web services, .Net Remoting, COM+, etc. WCF achieves this by configuring binding attributes of an endpoint. WCF lets you choose HTTP or TCP transport protocol, encoding, etc. just by tweaking the value of binding attribute for an endpoint.
 
To cater to different transport protocols, WCF lets you select HTTP, TCP and MSMQ binding types. For the purpose of this article, we are going to concentrate on HTTP and TCP binding with a concise explanation and simple example settings. 
 

basicHttpBinding

 
This type of binding exists in new .Net world only to support backward compatibility with ASMX based clients (WS-Basic Profile 1.1). Basic http binding sends SOAP 1.1 messages and is used when there is a requirement for the WCF services to communicate with non WCF based systems. Thus, providing an endpoint with basicHttpBinding makes interoperating with other basic implementations of web services a great choice.
 
Note: All other bindings except basicHttpBinding support WS* specifications including security, reliable messaging and transaction support, where appropriate.
 
How to setup the basicHttpBinding?
 
Let us examine how to setup binding for an endpoint in the web.config file. 
 
Step 1: Choose basicHttpBinding as a value in the binding attribute of an endpoint. 
  1. <endpoint   
  2. address="http://localhost:8731/EmployeeWCFService.ServiceImplementation.Manager/"  
  3. binding="basicHttpBinding"    
  4. bindingConfiguration="basicBinding"  
  5. contract=" EmployeeWCFService.ServiceContract.IEmployee">  
Step 2: This step is optional and is only required if the binding's default properties need to be modified, as shown in the example below. In this case, name the binding same as bindingConfiguration attribute in the endpoint section.
  1. <bindings>  
  2. <basicHttpBinding>  
  3.             <binding    name="basicBinding"   
  4. textEncoding="utf-8"   
  5. openTimeout="00:03:00"  
  6. closeTimeout="00:03:00"  
  7. />  
  8. </basicHttpBinding>             
  9. </bindings>  
Note: All other types of binding are setup in the same way.
 

wsHttpBinding

 
This binding sends SOAP 1.2 messages and implements WS* specifications to support enterprise requirements of security, reliability, ordered delivery and transaction management.
 

netTcpBinding

 
This binding sends SOAP 1.2 messages, provides binary encoding and optimized communication between WCF services and WCF clients on Windows network. This binding is the fastest binding amongst all WCF binding options between different nodes in the TCP network. Unlike http bindings, the TCP binding does not offer interoperability but is highly optimized for .Net 3.0 and above clients. Thus, in .Net version 3.0 and above, providing an endpoint with netTcpBinding is an easy option to development of distributed systems and can replace COM+ and .Net Remoting model.
 

netNamedPipeBinding

 
This binding is used to provide secure and reliable Named Pipe based communication between WCF services and WCF client on the same machine. It is the ideal choice for communication between processes on the same machine.
 

netPeerTcpBinding

 
This type of binding exists to cater peer-to-peer computing using WCF services.
 
For more information on PNRP visit Microsoft page Peer Name Resolution Protocol
 
How to setup the netPeerTcpBinding?
 
Let us examine how to setup netPeerTcpBinding for an endpoint in the web.config file.
 
Step 1: Before peer-to-peer binding can be used, make sure you have Peer Name Resolution Protocol installed on your machine. To enable PNRP on your Windows XP SP2 and above, take following steps: 
  • Go to Add or Remove Programs in the Control Panel
  • Select Add/Remove Windows Components option
  • Select Networking Services from the list of Components and click Details button
  • Select Peer-to-Peer option from the list, as shown in the screenshot, and click the OK button

    Figure4.gif

    Additionally, you can also make sure that the PNRP and its dependent services are started as follows:

    Figure5.gif
Step 2: Choose netPeerTcpBinding as a value in the binding attribute of an endpoint.
  1. <endpoint   
  2. address="net.p2p://localhost/MemberWCFService.ServiceImplementation.Member/"  
  3. binding="netPeerTcpBinding"    
  4. bindingConfiguration="netp2pBinding"  
  5. contract="MemberWCFService.ServiceContract.IMember">  
Step 3: To configure the binding as shown in the example below.
  1. <bindings>  
  2.       <netPeerTcpBinding>  
  3.         <binding name="netP2P" >  
  4.           <resolver mode="Pnrp" />  
  5.           <security mode="None" />  
  6.         </binding>  
  7. </netPeerTcpBinding>  
  8. </bindings>  
Thumb rules in choosing endpoint' binding
  • If you require your service to be consumed by clients compatible with SOAP 1.1, use basicHttpBinding for interoperability
  • If you require your service to be consumed within the corporate network, use netTCPBinding for performance
  • If you require your service to be consumed over the internet and the client is a WCF compatible, use wsHttpBinding to reap full benefits of WS* specifications
  • If you require your service to be accessible only in the same machine, use netNamedPipeBinding
  • If you require your service to be queue messages, use netMsmqBinding
  • If you require your service to act as server as well as client in a peer to peer environment, utilise netPeerTcpBinding setting

Binding configuration summary

 
Following table shows parameters such as security, transport protocol, encoding and hosting environment choices available with different binding for a WCF service. This summary should help choose an appropriate binding for your project environment. 
 
Binding Security
Default Configurable		 Transport Protocol Encoding
Default Other		 Host
basicHttpBinding None,
Transport, Message, Mixed		 HTTP Text/XML, MTOM IIS, WAS
wsHttpBinding Message, Transport, Mixed HTTP Text/XML, MTOM IIS, WAS
netTcpBinding Transport, Message, Mixed TCP Binary WAS
netNamedPipeBinding Transport,None Named Pipe Binary WAS
netMsmqBinding Message, Transport, None TCP Binary WAS
netPeerTcpBinding Transport P2P Binary -
 

FAQ about an Endpoint

 
Can I have multiple endpoints for a WCF service?
Answer: Yes
 
Can I have multiple endpoints of the same binding type e.g. multiple endpoints of basicHttpBinding?
Answer: Yes
 
Can I have multiple endpoints of different binding types to serve different types of clients e.g. an endpoint with basicHttpBinding, an endpoint with wsHttpBinding and an endpoint with netTcpBinging?
Answer: Yes
 

Summary

 
As you have seen, Windows Communication Foundation provides a framework to configure the transport, security and encoding needs to cater various communication requirements. The WCF framework keeps the development API same irrespective of the way it is going to be consumed by the clients. And, the endpoint is provided to meet the communication requirements, and you can have one or many of them to cater to different clients and communication requirements. This eliminates the need to learn and implement diverse set of communication models to support HTTP or TCP communication infrastructures. 


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