Question

我正在使用异步方法为UDP处理多个客户端的游戏创建一个服务器，并专门研究干净的断开逻辑。当客户端硬崩溃（他们的程序没有正确的断开逻辑而关闭）时，服务器上的readCallback会抛出SocketException

远程主机强行关闭现有连接

这是有道理的，但是当下次在read的循环中触发读取时，它会崩溃，尽管在回调中处理了异常。

    private void connectedState()
    {
        while (connected)
        {
            //reset the trigger to non-signaled
            readDone.Reset();

            read(socket);

            //block on reading data
            readDone.WaitOne();
        }
    }


    private void read(Socket sock)
    {
        // Creates an IpEndPoint to capture the identity of the sending host.
        IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
        EndPoint senderRemote = sender;

        // Create the state object.
        StateObject state = new StateObject();
        state.workSocket = sock;

        //crashes after an exception is caught within the callback
        sock.BeginReceiveFrom(state.buffer, 0, StateObject.MESSAGE_SIZE, SocketFlags.None, ref senderRemote, new AsyncCallback(readCallback), state);
    }


    private void readCallback(IAsyncResult ar)
    {
        StateObject state = (StateObject)ar.AsyncState;
        Socket sock = state.workSocket;

        EndPoint senderRemote = new IPEndPoint(IPAddress.Any, 0);

        try
        {
            // Read data from the client socket. 
            int bytesRead = sock.EndReceiveFrom(ar, ref senderRemote);

            if (bytesRead <= 0)
            {
                //handle disconnect logic
            }
            else
            {
                //handle the message received
            }
        }
        catch (SocketException se)
        {
            Console.WriteLine(se.ToString());
        }

        // Signal the read thread to continue
        readDone.Set();
    }

抛出两个例外，我相信其中一个被抓住了：

抛出异常：＆＃39; System.Net.Sockets.SocketException＆＃39;在System.dll中 System.Net.Sockets.SocketException（0x80004005）：远程主机强制关闭现有连接在System.Net.Sockets.Socket.EndReceiveFrom（IAsyncResult asyncResult，EndPoint＆amp; endPoint）在CardCatacombs.Utilities.Networking.UDPNetworkConnection.readCallback（IAsyncResult ar）中的C：\ Users \ kayas \ Desktop \ Practicum \ Source \ CardCatacombs \ CardCatacombs \ Utilities \ Networking \ UDPNetworkConnection.cs：line 424

抛出异常：＆＃39; System.Net.Sockets.SocketException＆＃39;在System.dll中 System.Net.Sockets.SocketException（0x80004005）：远程主机强制关闭现有连接 at System.Net.Sockets.Socket.DoBeginReceiveFrom（Byte [] buffer，Int32 offset，Int32 size，SocketFlags socketFlags，EndPoint endPointSnapshot，SocketAddress socketAddress，OverlappedAsyncResult asyncResult）

我希望能够干净地处理客户端崩溃并继续运行，因为还有其他客户端连接到服务器。

Answer 1

从this forum thread开始，UDP套接字似乎也在接收ICMP消息并抛出异常。如果端口不再侦听（在硬崩溃后），ICMP消息将导致“强制关闭”异常。

如果不需要，可以在创建UdpClient时使用以下代码禁用此异常，如上文所述：

public const int SIO_UDP_CONNRESET = -1744830452;
var client = new UdpClient(endpoint);
client.Client.IOControl(
    (IOControlCode)SIO_UDP_CONNRESET, 
    new byte[] { 0, 0, 0, 0 }, 
    null
);

C＃UDP远程主机

1 个答案: