Services and the WCF - Exposing Service Endpoints
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Endpoints expose service functionality at a particular address. Each endpoint is associated with a particular contract and a set of protocols as defined by the binding configuration. For each service, one or more endpoints may be exposed if multiple contracts are present or if multiple protocols are desired to access service functionality. Figure 1-20 illustrates how the ServiceHost instance exposes endpoints to clients and how the proxy invokes service operations at a particular endpoint.
Figure 1-20. ServiceHost exposes endpoints, and client proxies target a specific endpoint
As the lab illustrates, to create a service endpoint you provide an address, a binding, and a contract.
Addresses
The address can be a complete URI or a relative address like that used in the lab. The following shows you how to initialize an endpoint with a complete URI without supplying a base address to the ServiceHost:
using (ServiceHost host = new ServiceHost(typeof(HelloIndigo.HelloIndigoService)))
{
host.AddServiceEndpoint(typeof(HelloIndigo.IHelloIndigoService),
new BasicHttpBinding(), http://localhost:8000/HelloIndigo/ HelloIndigoService);
// other code
}
If you supply a relative address it is concatenated with theServiceHost base address for the matching protocol. The following illustrates providing an HTTP base address to theServiceHostconstructor and providing a relative address toAddServiceEndpoint():
using (ServiceHost host = new ServiceHost(typeof(HelloIndigo.HelloIndigoService),
new Uri(http://localhost:8000/HelloIndigo)))
{
host.AddServiceEndpoint(typeof(HelloIndigo.IHelloIndigoService),
new BasicHttpBinding(), "HelloIndigoService");
// other code
}
// Resulting endpoint address
http://localhost:8000/HelloIndigo/ HelloIndigoService
In practice, a base address should be supplied for each transport protocol over which the service can be accessed--for example, HTTP, TCP, named pipes, or MSMQ. In the event an endpoint address includes a complete URI, the base address will be ignored.
Using relative endpoint addressing makes is possible to modify the base URI to move all associated relative endpoints to a new domain or port. This can simplify the deployment process.
Bindings
The binding provided to an endpoint can be any of the standard bindings supplied by the service model. In this example, a new instance of the standard BasicHttpBinding is used to initialize the endpoint:
host.AddServiceEndpoint(typeof(HelloIndigo.IHelloIndigoService),
new BasicHttpBinding(), "HelloIndigoService");
The choice of binding defines the communication channel. For an endpoint,BasicHttpBinding, for example, supports requests over HTTP protocol sent in text format without any additional protocols for addressing, reliable messaging, security, or transactions.
In this chapter, you will employ other standard bindings, but you should look to Chapter 3 for an in-depth discussion of bindings, channels, and overall service model architecture.
Contracts
Each endpoint is associated with a particular service contract that determines the operations available at the endpoint. Only one service contract exists in this lab, but a service with multiple contracts could expose a different endpoint for each contract it wants to make accessible to clients.
Next: Creating a Client Proxy >>
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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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