Question

我有一个示例服务来测试WCF net.tcp通信。这是一个非常简单的服务，它所做的只是订阅客户端到服务，然后调用callbackchannel来通知所有连接的客户端有关广播的消息。该服务托管在IIS 7.5中。

这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);
}

以下是服务实施：

[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));
    }
}

我无法理解运行它时的行为。在第一个客户端运行后，一切正常，但当我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。

这是示例测试客户端：

    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);
        }
    }

当我运行5个客户端时，情况甚至出现问题。不是那些发送或接收消息。

Answer 1

当客户端调用SubcribeToService时，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，在所有收集的操作上下文中为每个已连接的客户端调用方法NotifyClient。

问题是，断开连接的客户端不会从JoinedClien列表中删除。当您尝试在断开连接的操作上下文上调用操作方法时，会出现通道处于故障状态错误。

要解决此问题，您应该订阅Channel_Closed和Channel_Faulted事件，并在回调客户端时删除CommunicationException并删除故障客户端的操作上下文：< / p>

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);
        }
    }
}

添加新客户端时，您也必须锁定该操作：

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

WCF双工TCP通信错误

1 个答案: