如何正常关闭异步服务器套接字？ C＃

Question

我已经看到很多关于在没有对象处理异常的情况下处理套接字的问题，所以我决定对它进行一次破解，看看是否可以完成。以下是我的发现。

问题？

您有一段代码使用来自System.Net.Sockets的Socket作为服务器套接字。问题是你想要关闭套接字，每次尝试时都会遇到ObjectDisposedException。

您的代码可能如下所示：

    private static ManualResetEvent allDone = new ManualResetEvent(false);
    private Socket ear;
    public void Start()
    {
        new Thread(() => StartListening()).Start();
    }

    private void StartListening()
    {
        IP = Dns.GetHostAddresses(Dns.GetHostName()).Where(address => address.AddressFamily == AddressFamily.InterNetwork).First();
        port = 11221;
        IPEndPoint localEndPoint = new IPEndPoint(IP, Port);
        ear = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        ear.Bind(localEndPoint);
        ear.Listen(100);
        try
        {

            while (true)
            {
                allDone.Reset();
                ear.BeginAccept(new AsyncCallback(AcceptCallback), ear);
                allDone.WaitOne();
            }
        }
        catch (ObjectDisposedException e)
        {
            Console.WriteLine("Socket Closed");
        }
    }

    private void AcceptCallback(IAsyncResult ar)
    {
        allDone.Set();
        Socket listener = (Socket)ar.AsyncState;
        Socket handler = listener.EndAccept(ar);

        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;

        StateObject state = (StateObject) ar.AsyncState;
        Socket handler = state.workSocket;

        int bytesRead = handler.EndReceive(ar);

        if (bytesRead > 0) {
            state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead));

            content = state.sb.ToString();
            if (content.IndexOf("<EOF>") > -1) {
                Console.WriteLine("Read {0} bytes from socket. \n Data : {1}", content.Length, content );
            } 
            else 
            {
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            }
        }
    }

    public void Stop()
    {
        ear.Close();
    }

运行类似于上面的代码会在AcceptCallback中尝试结束接收时出错。即使你抓住了它，你仍然会在StartListening（）方法中出现错误。

Answer 1

以下是我修复它的方法：

首先，我添加了一个名为IsListening的布尔值。

接下来，我改变了让耳朵听到While（IsListening）的条件。

在stop方法中，我在调用ear.close（）之前将IsListening变量设置为false，最后我在Manual SetEvent之后检查AcceptCallback内部的ear。

最终结果如下：

    private static ManualResetEvent allDone = new ManualResetEvent(false);
    private Socket ear;
    public void Start()
    {
        new Thread(() => StartListening()).Start();
    }

    private void StartListening()
    {
        IP = Dns.GetHostAddresses(Dns.GetHostName()).Where(address => address.AddressFamily == AddressFamily.InterNetwork).First();
        port = 11221;
        IPEndPoint localEndPoint = new IPEndPoint(IP, Port);
        ear = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        ear.Bind(localEndPoint);
        ear.Listen(100);

        IsListening = true;

        while (IsListening)
        {
            allDone.Reset();
            ear.BeginAccept(new AsyncCallback(AcceptCallback), ear);
            allDone.WaitOne();
        }
        Console.WriteLine("Socket Closed");
    }

    private void AcceptCallback(IAsyncResult ar)
    {
        allDone.Set();
        if (IsListening == false) return;
        Socket listener = (Socket)ar.AsyncState;
        Socket handler = listener.EndAccept(ar);

        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;

        StateObject state = (StateObject) ar.AsyncState;
        Socket handler = state.workSocket;

        int bytesRead = handler.EndReceive(ar);

        if (bytesRead > 0) {
            state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead));

            content = state.sb.ToString();
            if (content.IndexOf("<EOF>") > -1) {
                Console.WriteLine("Read {0} bytes from socket. \n Data : {1}", content.Length, content );
            } 
            else 
            {
                handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
            }
        }
    }

    public void Stop()
    {
        IsListening = false;
        ear.Close();
    }

异常现在已经消失。我希望这有助于其他人！