c# - 如何在单独的线程中正确关闭异步套接字监听器？

Question

我使用 C# 类来连接不同的子窗体。 项目是 MDI 类型。 在connection表单中，有一个线程调用的Asynchronous Socket Listner。 当我关闭我的应用程序时，我无法关闭监听器并且程序保留在任务管理器中。 问题与打开的监听器有关。 在表单连接中放置此代码:

 private AsynchronousSocketListener socketListener;          // Per socket in ascolto da parte delle App to Machine
    private Thread t_listener;

    public c_masterConn() //Costructor
    {
        socketListener = new AsynchronousSocketListener();          // Socketlistner async
        t_listener = new Thread(socketListener.StartListening);     // Thread for socketlistener
        t_listener.Start();                                         // Start socketlistener
    }

    public void StopThr() //Stop listner thread
    {
        t_listener.Interrupt();
    }

    public class AsynchronousSocketListener
    {
        // Thread signal.
        public static ManualResetEvent allDone = new ManualResetEvent(false);

        public AsynchronousSocketListener()
        {
        }

        public void StartListening()
        {
            // Data buffer for incoming data.
            byte[] bytes = new Byte[1024];

            // Establish the local endpoint for the socket.
            // The DNS name of the computer
            // running the listener is "host.contoso.com".
            IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
            IPAddress ipAddress = ipHostInfo.AddressList[0];
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);

            // Create a TCP/IP socket.
            Socket listener = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp);

            // Bind the socket to the local endpoint and listen for incoming connections.
            try
            {
                listener.Bind(localEndPoint);
                listener.Listen(100);

                while (true)
                {
                    // Set the event to nonsignaled state.
                    allDone.Reset();

                    // Start an asynchronous socket to listen for connections.
                    //Console.WriteLine("Waiting for a connection...");
                    listener.BeginAccept(
                        new AsyncCallback(AcceptCallback),
                        listener);

                    // Wait until a connection is made before continuing.
                    allDone.WaitOne();
                }

            }
            catch (Exception e)
            {
                //Console.WriteLine(e.ToString());
            }

            //Console.WriteLine("\nPress ENTER to continue...");
            //Console.Read();

        }

        public static void AcceptCallback(IAsyncResult ar)
        {
            // Signal the main thread to continue.
            allDone.Set();

            // Get the socket that handles the client request.
            Socket listener = (Socket)ar.AsyncState;
            Socket handler = listener.EndAccept(ar);

            // Create the state object.
            StateObject state = new StateObject();
            state.workSocket = handler;
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
        }

        public static void ReadCallback(IAsyncResult ar)
        {
            String content = String.Empty;

            // Retrieve the state object and the handler socket
            // from the asynchronous state object.
            StateObject state = (StateObject)ar.AsyncState;
            Socket handler = state.workSocket;

            // Read data from the client socket. 
            int bytesRead = handler.EndReceive(ar);

            if (bytesRead > 0)
            {
                // There  might be more data, so store the data received so far.
                state.sb.Append(Encoding.ASCII.GetString(
                    state.buffer, 0, bytesRead));

                // Check for end-of-file tag. If it is not there, read 
                // more data.
                content = state.sb.ToString();
                if (content.IndexOf("<EOF>") > -1)
                {
                    // All the data has been read from the 
                    // client. Display it on the console.
                    //Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
                    //    content.Length, content);
                    // Echo the data back to the client.
                    Send(handler, content);
                }
                else
                {
                    // Not all data received. Get more.
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReadCallback), state);
                }
            }
        }

        private static void Send(Socket handler, String data)
        {
            // Convert the string data to byte data using ASCII encoding.
            byte[] byteData = Encoding.ASCII.GetBytes(data);

            // Begin sending the data to the remote device.
            handler.BeginSend(byteData, 0, byteData.Length, 0,
                new AsyncCallback(SendCallback), handler);
        }

        private static void SendCallback(IAsyncResult ar)
        {
            try
            {
                // Retrieve the socket from the state object.
                Socket handler = (Socket)ar.AsyncState;

                // Complete sending the data to the remote device.
                int bytesSent = handler.EndSend(ar);
                //Console.WriteLine("Sent {0} bytes to client.", bytesSent);

                handler.Shutdown(SocketShutdown.Both);
                handler.Close();

            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }
        }
        public void StopListening() // Stop Listening
        {
            allDone.Close();
        }
    }

在 child 的形式中，我放了这个:

 private void hideMonBt_Click(object sender, EventArgs e)
    {
        this.Hide();
        m_engMonitor.m_masterConn.StopThr(); // Stop "server"
    }

    private void c_frmMonitor_Load(object sender, EventArgs e)
    {
        m_engMonitor.socketConnect(); // Start "server" connection
    }

我不确定在连接中使用这段代码:

  public void StopListening() // Stop Listening
        {
            allDone.Close();
        }

 public void StopThr() //Stop listner thread
    {
        t_listener.Interrupt();
    }

我做错了什么？ 谢谢。

Answer 1

问题是你永远不会停止倾听。您正在无限循环中运行套接字，当您想要结束它时，您并没有关闭套接字，而是中断了线程。这相当于通过敲门离开您的房子，而不是打开它并在您身后关上它。

为了正确地停止收听，您关闭套接字。当发生这种情况时，BeginAccept 将抛出一个 ObjectDisposedException。根本不需要中断您的线程:

public class AsynchronousSocketListener : IDisposable
{
    Socket listener;
    // Thread signal.
    public ManualResetEvent allDone = new ManualResetEvent(false);

    public AsynchronousSocketListener()
    {
    }

    public void StartListening()
    {
        // Data buffer for incoming data.
        byte[] bytes = new Byte[1024];

        // Establish the local endpoint for the socket.
        // The DNS name of the computer
        // running the listener is "host.contoso.com".
        IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
        IPAddress ipAddress = ipHostInfo.AddressList[0];
        IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);

        // Create a TCP/IP socket.
        listener = new Socket(AddressFamily.InterNetwork,
            SocketType.Stream, ProtocolType.Tcp);

        // Bind the socket to the local endpoint and listen for incoming connections.
        try
        {
            listener.Bind(localEndPoint);
            listener.Listen(100);

            while (true)
            {
                // Set the event to nonsignaled state.
                allDone.Reset();

                // Start an asynchronous socket to listen for connections.
                //Console.WriteLine("Waiting for a connection...");
                listener.BeginAccept(
                    new AsyncCallback(AcceptCallback),
                    listener);

                // Wait until a connection is made before continuing.
                allDone.WaitOne();
            }

        }
        catch (ObjectDisposedException)
        {
            //Console.WriteLine("Listener closed.");
        }
        catch (Exception e)
        {
            //Console.WriteLine(e.ToString());
        }

        //Console.WriteLine("\nPress ENTER to continue...");
        //Console.Read();

    }

    //...

    public void StopListening() // Stop Listening
    {
        Socket exListener = Interlocked.Exchange(ref listener, null);
        if (exListener != null)
        {
            exListener.Close();
        }
    }

    public void Dispose()
    {
        StopListening();
    }
}

当你想结束监听时，只需调用StopListening。当StartListening退出时，线程将正常结束。

我对您的代码所做的一些其他更改:

• 我制作了 AsynchronousSocketListener 一次性的。您正在包装一个套接字，您需要确保在处理您的监听器时释放它。
• 将 allDone 从 static 更改为实例。如果您有多个监听器(例如，不同的端口)，他们会共享事件，这是一个错误。

您还需要做的:如果您在StartListening 分配listener 的值之前调用StopListening，监听将不会停止。监听器将正常启动。这是您必须消除的代码中的竞争条件。