[原创]我的WCF之旅（2）：Endpoint Overview

WCF实际上是构建了一个框架，这个框架实现了在互联系统中各个Application之间如何通信。使得Developers和Architect在构建分布式系统中，无需在考虑如何去实现通信相关的问题，更加关注与系统的业务逻辑本身。而在WCF Infrastructure中，各个Application之间的通信是由Endpoint来实现的。

Endpoint的结构

Endpoint包含以下4个对象：

• Address: Address通过一个URI唯一地标识一个Endpoint，并告诉潜在的WCF service的调用者如何找到这个Endpoint。所以Address解决了Where to locate the WCF Service？
• Binding: Binding实现在Client和Service通信的所有底层细节。比如Client与Service之间传递的Message是如何编码的——text/XML, binary，MTOM；这种Message的传递是采用的哪种Transport——TCP, Http, Named Pipe, MSMQ; 以及采用怎样的机制解决Secure Messaging的问题——SSL，Message Level Security。所以Binding解决的是How to communicate with service？
• Contract: Contract的主要的作用是暴露某个WCF Service所提供的所有有效的Functionality。从Message Exchange的层面上讲，Contract实际上是抱每个Operation转化成为相对应的Message Exchange Pattern——MEP（Request/Response； One-way； Duplex）。所以Contract解决的是What functionalities do the Service provide？
•  Behavior: Behavior的主要作用是定制Endpoint在运行时的一些必要的Behavior。比如Service 回调Client的Timeout；Client采用的Credential type；以及是否支持Transaction等。

当我们Host一个WCF Service的时候，我们必须给他定义一个或多个Endpoint，然后service通过这个定义的Endpoint进行监听来自Client端的请求。当我们的Application需要调用这个Service的时候，因为Client 和Service是通过Endpoint的进行通信的， 所以我们必须为我们的Application定义Client端的Endpoint。只有当Client的Endpoint和Service端某个Endpoint相互匹配（Service端可以为一个Service定义多个Endpoint），Client端的请求才能被Service端监听到。也就是说，我们只有在Client具有一个与Service端完全匹配的Endpoint，我们才能调用这个Service。而这种匹配是比较严格的，比如从匹配Address方面，Client端和Service端的Endpoint Address不仅仅在URI上要完全匹配Service， 他们的Headers也需要相互匹配。对于Binding, 一般地，Client需要有一个与Service端完全一样的Binding，他们之间才能通信。 

Sample

首先给一个Sample，以便我们对在WCF Service Aplication中如何定义Endpoint有一个感性的认识。整个Solution的结构参照下图，我的上一篇Blog([原创]我的WCF之旅（1）：创建一个简单的WCF程序 )中有详细的介绍。你也可以通过后面的Link下载相应的Source Code（http://www.cnblogs.com/files/artech/Artech.WCFService.zip ）

1． Service Contract：Artech..WCfService.Contract/ServiceContract/IGeneralCalculator.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;

namespace Artech.WCFService.Contract
{
    [ServiceContract]
    public interface IGeneralCalculator
    {
        [OperationContract]
        double Add(double x, double y);
    }
}

2. Service: Artech.WCFSerice.Service/GeneralCalculatorService.cs

using System;
using System.Collections.Generic;
using System.Text;

using Artech.WCFService.Contract;

namespace Artech.WCFService.Service
{
    public class GeneralCalculatorService:IGeneralCalculator
    {
        IGeneralCalculator Members#region IGeneralCalculator Members

        public double Add(double x, double y)
        {
            return x + y;
        }

        #endregion
    }
}

3. Hosting: Artech.WCFService.Hosting/Program.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
using Artech.WCFService.Contract;
using Artech.WCFService.Service;
using System.ServiceModel.Description;

namespace Artech.WCFService.Hosting
{
    class Program
    {
        static void Main(string[] args)
        {
            //HostCalculatorServiceViaCode();
            HostCalculatorSerivceViaConfiguration();
        }

        /**//// <summary>
        /// Hosting a service using managed code without any configuraiton information. 
        /// Please note that the related configuration data should be removed before calling the method.
        /// </summary>
        static void HostCalculatorServiceViaCode()
        {
            Uri httpBaseAddress = new Uri("http://localhost:8888/generalCalculator");
            Uri tcpBaseAddress = new Uri("net.tcp://localhost:9999/generalCalculator");
            
            using (ServiceHost calculatorSerivceHost = new ServiceHost(typeof(GeneralCalculatorService), httpBaseAddress, tcpBaseAddress))
            {           
                BasicHttpBinding httpBinding = new BasicHttpBinding();
                NetTcpBinding tcpBinding = new NetTcpBinding();

                calculatorSerivceHost.AddServiceEndpoint(typeof(IGeneralCalculator), httpBinding, string.Empty);
                calculatorSerivceHost.AddServiceEndpoint(typeof(IGeneralCalculator), tcpBinding, string.Empty);

                ServiceMetadataBehavior behavior = calculatorSerivceHost.Description.Behaviors.Find<ServiceMetadataBehavior>();
                {
                    if(behavior == null)
                    {
                        behavior = new ServiceMetadataBehavior();
                        behavior.HttpGetEnabled = true;
                        calculatorSerivceHost.Description.Behaviors.Add(behavior);
                    }
                    else
                    {
                        behavior.HttpGetEnabled = true;
                    }
                }

                calculatorSerivceHost.Opened += delegate
                {
                    Console.WriteLine("Calculator Service has begun to listen  ");
                };

                calculatorSerivceHost.Open();

                Console.Read();
            }
        }

        static void HostCalculatorSerivceViaConfiguration()
        {
            using (ServiceHost calculatorSerivceHost = new ServiceHost(typeof(GeneralCalculatorService)))
            {               
                calculatorSerivceHost.Opened += delegate
                {
                    Console.WriteLine("Calculator Service has begun to listen  ");
                };

                calculatorSerivceHost.Open();

                Console.Read();
            }
        }        
    }
}

4. Service.svc: http://localhost/WCFService/ GeneralCalculatorService.svc

<%@ ServiceHost Language="C#" Debug="true" Service="Artech.WCFService.Service.GeneralCalculatorService" %>

5. Client: Artech.WCFService.Client/ GeneralCalculatorClient.cs & Program.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Channels;
using Artech.WCFService.Contract;

namespace Artech.WCFService.Client
{
    class GeneralCalculatorClient:ClientBase<IGeneralCalculator>,IGeneralCalculator
    {
        public GeneralCalculatorClient()
            : base()
        { }

        public GeneralCalculatorClient(string endpointConfigurationName)
            : base(endpointConfigurationName)
        { }

        public GeneralCalculatorClient(Binding binding, EndpointAddress address)
            : base(binding, address)
        { }

        IGeneralCalculator Members#region IGeneralCalculator Members

        public double Add(double x, double y)
        {
            return this.Channel.Add(x, y);
        }

        #endregion
    }
}

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Channels;

using Artech.WCFService.Contract;

namespace Artech.WCFService.Client
{
    class Program
    {
        static void Main()
        {
            try
            {
                //InvocateCalclatorServiceViaCode();

                InvocateCalclatorServiceViaConfiguration();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }

            Console.Read();    
        }

        static void InvocateCalclatorServiceViaCode()
        {
            Binding httpBinding = new BasicHttpBinding();
            Binding tcpBinding = new NetTcpBinding();

            EndpointAddress httpAddress = new EndpointAddress("http://localhost:8888/generalCalculator");
            EndpointAddress tcpAddress = new EndpointAddress("net.tcp://localhost:9999/generalCalculator");
            EndpointAddress httpAddress_iisHost = new EndpointAddress("http://localhost/wcfservice/GeneralCalculatorService.svc");

            Console.WriteLine("Invocate self-host calculator service ");

            Invocate Self-host service#region Invocate Self-host service
            using (GeneralCalculatorClient calculator_http = new GeneralCalculatorClient(httpBinding, httpAddress))
            {
                using (GeneralCalculatorClient calculator_tcp = new GeneralCalculatorClient(tcpBinding, tcpAddress))
                {
                    try
                    {
                        Console.WriteLine("Begin to invocate calculator service via http transport ");
                        Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_http.Add(1, 2));

                        Console.WriteLine("Begin to invocate calculator service via tcp transport ");
                        Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator_tcp.Add(1, 2));
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine(ex.Message);
                    }
                }
            }
            #endregion

            Console.WriteLine("\n\nInvocate IIS-host calculator service ");

            Invocate IIS-host service#region Invocate IIS-host service
            using (GeneralCalculatorClient calculator = new GeneralCalculatorClient(httpBinding, httpAddress_iisHost))
            {
                try
                {
                    Console.WriteLine("Begin to invocate calculator service via http transport ");
                    Console.WriteLine("x + y = {2} where x = {0} and y = {1}", 1, 2, calculator.Add(1, 2));
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.Message);
                }
            }
            #endregion
        }

        static void InvocateCalclatorServiceViaConfiguration()
        {
            Console.WriteLine("Invocate self-host calculator service ");

            Invocate Self-host service#region Invocate Self-host service
            using (GeneralCalculatorClient calculator_http = new GeneralCalculatorClient("selfHostEndpoint_http"))
            {
                using (GeneralCalculatorClient calculator_tcp = new GeneralCalculatorClient("selfHostEndpoint_tcp"))