在WCF通信中,如果实现要得到服务端处理的结果,一种方式是在契约中指定调用方法带返回值(IsOneWay=false),但这种方式是有缺陷的,如果服务端处理时间过长,则客户端也需要长时间等待。
另一种方式是通过双工通信,使用回调来实现。但回调的时候,回调方法中不应该有耗时操作,否则当服务端处理完成退出的时间,回调消息会丢失。
目前WCF支持双工的绑定方式有:WSDualHttpBinding,NetTcpBinding与NetNamedPipeBinding三种,其它绑定方式不支持双工。
下面以一个简短的例子说明双工通信。
1、定义契约
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- [ServiceContract(Namespace = "http://cnblog.com/zhili/", CallbackContract = typeof(ICallback))]
- public interface ICalculator
- {
- [OperationContract(IsOneWay = true)]
- void Multiple(double a, double b);
- [OperationContract(IsOneWay = true)]
- void DisplayString(string name);
- }
其中指定了回调契约是ICallback。
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- // 回调契约的定义,此时回调契约不需要应用ServiceContractAttribute特性
- public interface ICallback
- {
- [OperationContract(IsOneWay = true)]
- void DisplayResult(double x, double y, double result);
- [OperationContract(IsOneWay = false, ProtectionLevel = ProtectionLevel.EncryptAndSign)]
- string DisplayStringResult(string retStr);
- }
我们看到,回调第二个方法有返回值。这个在服务行为配置中要有特殊配置,否则会卡死。
2、服务端实现
实现服务契约:
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- // 服务契约的实现
- [ServiceBehavior(IncludeExceptionDetailInFaults = true,ConcurrencyMode = ConcurrencyMode.Multiple)]
- public class CalculatorService : ICalculator
- {
- #region ICalculator Members
- public void Multiple(double a, double b)
- {
- for (int i = 1; i < 100; i++)
- {
- double result = a * b;
- // 通过客户端实例通道
- ICallback callback = OperationContext.Current.GetCallbackChannel<ICallback>();
- // 对客户端操作进行回调
- callback.DisplayResult(a, b, result);
- Console.WriteLine("Callback Times {0} at time {1}", i, DateTime.Now.ToString("hh:mm:ss tt zz"));
- }
- Program.ExitFlag = true;
- }
- public void DisplayString(string name)
- {
-
- for (int i = 1; i < 100; i++)
- {
- // 通过客户端实例通道
- ICallback callback = OperationContext.Current.GetCallbackChannel<ICallback>();
-
- // 对客户端操作进行回调
- string retStr = callback.DisplayStringResult("Hello " + name);
- Console.WriteLine("Callback Times {0} at time {1}, ret={2}", i, DateTime.Now.ToString("hh:mm:ss tt zz"), retStr);
- }
- Program.ExitFlag = true;
- }
- #endregion
- }
其中ServiceBehavior属性的ConcurrencyMode =ConcurrencyMode.Multiple配置就是配置回调方法带返回值问题(IsOneWay=false),如果不设置这个属性,或者设置为Single,上述回调方法调用时会卡死。
主程序如下:
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- class Program
- {
- public static bool ExitFlag = false;
- static void Main(string[] args)
- {
- using (ServiceHost host = new ServiceHost(typeof(CalculatorService)))
- {
- host.Opened += delegate
- {
- Console.WriteLine("Service start now....");
- };
- host.Open();
- while (!ExitFlag)
- {
- Thread.Sleep(500);
- }
- }
- }
- }
主程序配置(App.Config):
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- <?xml version="1.0" encoding="utf-8" ?>
- <configuration>
- <system.serviceModel>
- <behaviors>
- <serviceBehaviors>
- <behavior>
- <serviceMetadata httpGetEnabled="true" httpGetUrl="http://localhost:8080/Metadata"/>
- </behavior>
- </serviceBehaviors>
- </behaviors>
- <services>
- <service name="NMS.WCFDemo.Server.CalculatorService">
- <endpoint address="net.tcp://localhost:9003/CalculatorService" binding="netTcpBinding" contract="NMS.WCFDemo.Contract.ICalculator"/>
- </service>
- </services>
- </system.serviceModel>
- </configuration>
3、客户端
创建完客户端程序后,添加一个服务引用,指向上面配置文件的地址http://localhost:8080/Metadata获取服务引用。(添加服务引用时服务程序必须已经在运行)
实现回调契约:
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- // 客户端中对回调契约的实现
- public class CallbackWCFService : ICalculatorCallback
- {
- private int i = 1;
- public void DisplayResult(double a, double b, double result)
- {
- Console.WriteLine("{4} : {0} * {1} = {2} ====== AT Time {3}", a, b, result, DateTime.Now.ToString("hh:mm:ss tt zz"), i++);
- Thread.Sleep(1000);
- }
- public string DisplayStringResult(string retStr)
- {
- Console.WriteLine("{0} : recevie msg {1} ====== AT Time {2}", i++, retStr, DateTime.Now.ToString("hh:mm:ss tt zz"));
- Thread.Sleep(1000);
- return i.ToString();
- }
- }
客户端主程序:
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- // 客户端实现,测试回调操作
- class Program
- {
- static void Main(string[] args)
- {
- InstanceContext instanceContex = new InstanceContext(new CallbackWCFService());
- CalculatorClient proxy = new CalculatorClient(instanceContex);
- if (args[0] == "1")
- {
- proxy.Multiple(2, 3);
- }
- else
- {
- Console.WriteLine("Call string ...");
- proxy.DisplayString("Client");
- }
- Console.Read();
- }
- }
客户端配置文件(App.Config)
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- <?xml version="1.0" encoding="utf-8" ?>
- <configuration>
- <startup>
- <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
- </startup>
- <system.serviceModel>
- <bindings>
- <netTcpBinding>
- <binding name="NetTcpBinding_ICalculator" />
- <binding name="NetTcpBinding_ICalculator1" />
- </netTcpBinding>
- </bindings>
- <client>
- <endpoint address="net.tcp://localhost:9003/CalculatorService"
- binding="netTcpBinding" bindingConfiguration="NetTcpBinding_ICalculator"
- contract="NMS.WCFDemo.Contract.ICalculator" name="NetTcpBinding_ICalculator" />
- <endpoint address="net.tcp://localhost:9003/CalculatorService"
- binding="netTcpBinding" bindingConfiguration="NetTcpBinding_ICalculator1"
- contract="ServiceReference1.ICalculator" name="NetTcpBinding_ICalculator1">
- <identity>
- <userPrincipalName value="DESKTOP-4D9M16H\wangcc" />
- </identity>
- </endpoint>
- </client>
- </system.serviceModel>
- </configuration>
然后运行程序就能看到效果了。