WCF双工TCP通信错误

Question

我有一个示例服务来测试WCF net.tcp通信。这是非常简单的服务，它所做的只是向服务订阅客户端，然后调用callbackchannel来通知所有连接的客户端有关广播消息。该服务托管在IIS 7.5中。

这里是服务代码和测试客户端来测试它。

[ServiceContract(CallbackContract = typeof(ISampleServiceCallBack), SessionMode = SessionMode.Required)] 
public interface ISampleCuratioService 
{ 
    [OperationContract(IsOneWay = true)] 
    void SubcribeToService(string sub); 

    [OperationContract] 
    string GetData(int value); 

    [OperationContract(IsOneWay = true)] 
    void Broadcast(string message); 
} 

public interface ISampleServiceCallBack 
{ 
    [OperationContract(IsOneWay = true)] 
    void NotifyClient(string message); 
} 

这里的服务实现：

[ServiceBehavior(Name = "CuratioCSMService", InstanceContextMode = InstanceContextMode.PerSession)] 
public class Service1 : ISampleCuratioService 
{ 
    private static List<ISampleServiceCallBack> JoinedClien = new List<ISampleServiceCallBack>(); 

    public void SubcribeToService(string sub) 
    { 
     var subscriber = OperationContext.Current.GetCallbackChannel<ISampleServiceCallBack>(); 
     if (!JoinedClien.Contains(subscriber)) 
     { 
      JoinedClien.Add(subscriber); 
     } 
    } 

    public string GetData(int value) 
    { 
     return string.Format("You entered: {0}", value); 
    } 

    public void Broadcast(string message) 
    { 
     JoinedClien.ForEach(c => c.NotifyClient("message was received " + message)); 
    } 
} 

我不明白运行时，我得到它的行为。第一个客户端运行后，一切正常，但在关闭并打开测试客户端应用程序时，它会抛出异常，通知该通道不能用于通信，因为它处于故障状态。

这是样品测试客户端：当我运行5个客户

static void Main(string[] args) 
    { 
     var callneckclient = new ServiceClientProxy(); 
     var client = new SampleCuratioServiceClient(new InstanceContext(callneckclient)); 
     client.SubcribeToService("me"); 
     Console.ReadLine(); 

     for (int i = 0; i < 15; i++) 
     { 
      Console.WriteLine(client.GetData(5)); 
      client.Broadcast("this is from client me"); 
     } 
     client.Close(); 
     Console.Read(); 
    } 

    public class ServiceClientProxy : ISampleCuratioServiceCallback, IDisposable 
    { 
     public void NotifyClient(string message) 
     { 
      Console.WriteLine(message); 
     } 

     public void Dispose() 
     { 
      GC.SuppressFinalize(this); 
     } 
    } 

的情况就会更马车。不是那些发送或接收消息。

Answer 1

当客户端调用SubcribeToService时，您将其操作上下文添加到名为JoinedClien的列表中。

当您在服务器中调用Broadcast时，您将针对每个连接的客户端在所有收集的操作上下文中调用方法NotifyClient。

问题是，断开的客户端不会从您的JoinedClien列表中删除。 当您尝试调用断开的操作上下文的操作方法时，您会收到通道处于错误状态错误。

要解决，你应该订阅Channel_Closed和Channel_Faulted事件，还搭上CommunicationException回拨到您的客户端时，并移除故障客户端的操作语境：

public void Broadcast(string message) 
{ 
    // copy list of clients 
    List<OperationContext> clientsCopy = new List<OperationContext>(); 
    lock(JoinedClien) { 
     clientsCopy.AddRange(JoinedClien); 
    } 

    // send message and collect faulted clients in separate list 
    List<OperationContext> clientsToRemove = new List<OperationContext>(); 
    foreach (var c in JoinedClien) 
    { 
     try { 
      c.NotifyClient("message was received " + message)); 
     } 
     catch (CommunicationException ex) { 
      clientsToRemove.Add(c); 
     } 
    } 

    foreach (var c in clientsToRemove) 
    { 
     lock(JoinedClien) { 
      if(JoinedClien.Contains(c)) 
       JoinedClien.Remove(c); 
     } 
    } 
} 

当增加新客户你也必须锁定该操作：

var subscriber = OperationContext.Current.GetCallbackChannel<ISampleServiceCallBack>(); 
lock(JoinedClien) 
{ 
    if (!JoinedClien.Contains(subscriber)) 
    { 
     JoinedClien.Add(subscriber); 
    } 
}