Question

我有以下客户端侦听器将客户端传递给HandleStationClients。 HandleStationClients的构造函数启动一个Task，其他线程中的连接用于侦听。

下面的代码在主线程上运行，具有异步功能。当客户端连接下面的等待部分时，将继续并将客户端传递给新创建的HandleStationClients并挂钩事件。通常在连接事件之后，循环将重新开始并等待await处的新连接。问题是这个代码循环每次连接两次。因此客户端连接和HandleStationClients将被创建并且事件将被挂钩并且循环再次启动，然后继续运行相同的过程再次创建新的HandleStationClients和事件挂钩。

在处理客户端之后，等待者没有等待，而是继续第二次。事件被触发两次。我不知道什么是错的。任何人都有线索？

while (true)
{
    counter += 1;

    // Wait for new connection then do rest
    stationsClientSocket = await stationsServerSocket.AcceptTcpClientAsync();

    stationClients.Add(stationsClientSocket, 0);
    Debug.WriteLine("Client toegevoegd " + counter);

    HandleStationClients stationClient = new HandleStationClients(stationsClientSocket);

    stationClient.ConnectionEstabilished += stationClient_ConnectionEstabilished;
    stationClient.ConnectionClosed += stationClient_ConnectionClosed;
    stationClient.NewDataReceived += stationClient_NewDataReceived;
}

HandleClient看起来像

class HandleStationClients
{
    public HandleStationClients(TcpClient client)
    {
        Task.Factory.StartNew(() => { ProcessConnection(client); });
    }

    #region Event definitions
    public delegate void NewDataReceivedEventHandler(string newData);
    public event NewDataReceivedEventHandler NewDataReceived;

    public delegate void ConnectionClosedEventHandler();
    public event ConnectionClosedEventHandler ConnectionClosed;

    public delegate void ConnectionEstabilishedEventHandler(IPEndPoint endpoint);
    public event ConnectionEstabilishedEventHandler ConnectionEstabilished;
    #endregion

    public async void ProcessConnection(TcpClient stationsClientSocket)
    {
        byte[] message = new byte[1024];
        int bytesRead;

        NetworkStream networkStream = stationsClientSocket.GetStream();

        if (this.ConnectionEstabilished != null)
        {
            this.ConnectionEstabilished((IPEndPoint)stationsClientSocket.Client.RemoteEndPoint);
        }

        while ((true))
        {
            bytesRead = 0;

            try
            {
                bytesRead = await networkStream.ReadAsync(message, 0, 1024);
            }
            catch (Exception ex)
            {
                // some error hapens here catch it                    
                Debug.WriteLine(ex.Message);
                break;
            }

            if (bytesRead == 0)
            {
                //the client has disconnected from the server
                break;
            }

            ASCIIEncoding encoder = new ASCIIEncoding();

            if (this.NewDataReceived != null)
            {
                byte[] buffer = null;

                string incomingMessage = encoder.GetString(message, 0, bytesRead);

                this.NewDataReceived(incomingMessage);
            }
        }
        stationsClientSocket.Close();
        // Fire the disconnect Event
        this.ConnectionClosed();
    }
}

Answer 1

在构造函数中启动任务是个坏主意。这意味着您在注册事件处理程序时正在运行任务。有一个很好的机会，有时你不会在需要被解雇之前注册一个事件。

您应该做的是等待所有事件处理器全部注册之前启动任务。您需要创建一个Start方法来处理启动任务，并在事件注册后让代码调用它。

更新后的课程：

class HandleStationClients
{
    // Added a field to store the value until the Start method
    TcpClient _client;

    public HandleStationClients(TcpClient client)
    {
        this._client = client;
        // Moved the line from here...
    }

    public void Start()
    {
        // ...to here.
        Task.Factory.StartNew(() => { ProcessConnection(_client); });
    }

    #region Event definitions
    // ...
    #endregion

    public async void ProcessConnection(TcpClient stationsClientSocket)
    {
        byte[] message = new byte[1024];
        int bytesRead;

        NetworkStream networkStream = stationsClientSocket.GetStream();

        if (this.ConnectionEstabilished != null)
        {
            this.ConnectionEstabilished((IPEndPoint)stationsClientSocket.Client.RemoteEndPoint);
        }

        while ((true))
        {
            bytesRead = 0;

            try
            {
                bytesRead = await networkStream.ReadAsync(message, 0, 1024);
            }
            catch (Exception ex)
            {
                // some error hapens here catch it                    
                Debug.WriteLine(ex.Message);
                break;
            }

            if (bytesRead == 0)
            {
                //the client has disconnected from the server
                break;
            }

            ASCIIEncoding encoder = new ASCIIEncoding();

            if (this.NewDataReceived != null)
            {
                byte[] buffer = null;

                string incomingMessage = encoder.GetString(message, 0, bytesRead);

                this.NewDataReceived(incomingMessage);
            }
        }
        stationsClientSocket.Close();
        // Fire the disconnect Event
        // I added a line to check that ConnectionClosed isn't null
        if (this.ConnectionClosed != null)
        {
            this.ConnectionClosed();
        }
    }
}

然后您需要更改调用代码，如下所示。

while (true)
{
    counter += 1;

    // Wait for new connection then do rest
    stationsClientSocket = await stationsServerSocket.AcceptTcpClientAsync();

    stationClients.Add(stationsClientSocket, 0);
    Debug.WriteLine("Client toegevoegd " + counter);

    HandleStationClients stationClient = new HandleStationClients(stationsClientSocket);

    stationClient.ConnectionEstabilished += stationClient_ConnectionEstabilished;
    stationClient.ConnectionClosed += stationClient_ConnectionClosed;
    stationClient.NewDataReceived += stationClient_NewDataReceived;
    // Call Start manually
    stationClient.Start();
}

Answer 2

我将Task从构造函数移动到Start方法。问题解决了。

循环与异步等待操作怪异

2 个答案: