我的WCF之旅 (11): 再谈WCF的双向通讯-基于Http的双向通讯 V.S. 基于TCP的双向通讯


在一个基于面向服务的分布式环境中，借助一个标准的、平台无关的Communication Infrastructure，各个Service通过SOAP Message实现相互之间的交互。这个交互的过程实际上就是Message Exchange的过程。WCF支持不同形式的Message Exchange，我们把这称之为Message Exchange Pattern（MEP）, 常见的MEP包括: Request/Reply，Request/Forget（One-way）和Duplex。通过采用Duplex MEP，我们可以实现在Service端Callback Client的操作。虽然WCF为我们实现底层的通信细节，使得我们把精力转移到业务逻辑的实现，进行Transport无关的编程，但是对底层Transport的理解有利于我们根据所处的具体环境选择一个合适的Transport。说到Transport， WCF 经常使用的是以下4个：Http，TCP，Named Pipe，MSMQ。由于不同协议自身的差异，他们对具体MEP的支持方式也会不同，我们今天就来谈谈Http和TCP对Duplex的支持。 
一、Sample
为了使大家对在WCF如何实现双向通信（Bidirectional Communication）有一个直观的理解，我们先来看一个简单的Sample。我们照例采用下面的4层结构和Calculator的例子：

 

1．Contract：Artech.DuplexWCF.Contract. ICalculator

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
namespace Artech.DuplexWCF.Contract
{
    [ServiceContract(CallbackContract = typeof(ICallback))]
    public inte易做图ce ICalculator
    {
        [OperationContract(IsOneWay = true)]
        void Add(double x, double y);
    }
}
由于模拟的是通过Callback来显示Add方法计算的结果，我把Add Operation设置成One-way。在Service Contract中设置了Callback Contract，Callback Contract定义在Inte易做图ce Artech.DuplexWCF.Contract. ICallback中：
using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
namespace Artech.DuplexWCF.Contract
{
    [ServiceContract]
    public inte易做图ce ICallback
    {
        [OperationContract(IsOneWay = true)]
        void DisplayResult(double result);
    }
}
2．Service: Artech.DuplexWCF.Service. CalculatorService

using System;
using System.Collections.Generic;
using System.Text;
using Artech.DuplexWCF.Contract;
using System.ServiceModel;
namespace Artech.DuplexWCF.Service
{
    public class CalculatorService:ICalculator
    {
        ICalculator Members#region ICalculator Members
        public void Add(double x, double y)
        {
            double result = x + y; 
            ICallback callback = OperationContext.Current.GetCallbackChannel<ICallback>();
            callback.DisplayResult(result);
        }
        #endregion
    }
}
在Service端，通过OperationContext.Current.GetCallbackChannel来获得Ciient指定的CallbackContext instance，进而调用Client的Operation。
3．Hosting：
Configuration:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.serviceModel>        
        <services>
            <service name="Artech.DuplexWCF.Service.CalculatorService">
                <endpoint address="net.tcp://localhost:9999/calculator"  binding="netTcpBinding" contract="Artech.DuplexWCF.Contract.ICalculator" />                
            </service>
        </services>
    </system.serviceModel>
</configuration>
我们通过netTcpBinding来模拟基于TCP的双向通信。
Program：

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel;
using Artech.DuplexWCF.Service;
namespace Artech.DuplexWCF.Hosting
{
    class Program
    {
        static void Main(string[] args)
        {
            using (ServiceHost calculatorHost = new ServiceHost(typeof(CalculatorService)))
            {
                calculatorHost.Opened += delegate
                {
                    Console.WriteLine("The calculator service has begun to listen");
                };
                calculatorHost.Open();
                Console.Read();
            }
        }
    }
}
4．Client：
Configuration:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <system.serviceModel>
        <client>
            <endpoint address="net.tcp://localhost:9999/calculator" binding="netTcpBinding"
                bindingConfiguration="" contract="Artech.DuplexWCF.Contract.ICalculator"
                name="defaultEndpoint" />
        </client>
    </system.serviceModel>
</configuration>
Callback：Artech.DuplexWCF.Client. CalculatorCallback
 

using System;
using System.Collections.Generic;
using System.Text;
using Artech.DuplexWCF.Contract;
namespace Artech.DuplexWCF.Client
{
    public class CalculatorCallback:ICallback
    {
        ICallback Members#region ICallback Members
        public void DisplayResult(double result)
        {
            Console.WriteLine("The result is {0}", result);
        }
        #endregion
    }
}
Callback的操作-显示计算结果，实现在Artech.DuplexWCF.Client. CalculatorCallback中，他实现了在Contract中定义的Callback Contract：Artech.DuplexWCF.Contract. ICallback。
Program：

using System;
using System.Collections.Generic;
using System.Text;
using Artech.DuplexWCF.Contract;
using Sys

补充：综合编程 , 其他综合 ,