c# - C#:远程主机上的套接字ReceiveAsync和SendAsync出现问题

Question

首先，我想说的是，带有服务器/客户端的代码在我的PC上可以正常工作(客户端和服务器都在同一台PC上运行)

当我在专用服务器上托管服务器时，问题就开始了。第二次我尝试与客户端发送或接收时，客户端将花费很多时间来完成操作(谈论接收1个字节的数据需要花费超过1个小时的时间!)

**我可以通过在每次发送/接收命令后简单地断开并重新连接套接字来避免此问题

我不明白为什么如果我要在同一连接 session 中执行多于1个发送/接收操作的时间，那么为什么要花这么多时间。

这是一个例子:

连接服务器:

    RC_Server = new SocketConnection_Client(RC_IpEndPoint);

现在客户端已连接到服务器，并且我可以正常开始发送/接收。

我第一次尝试发送或接收它时，它的工作原理非常完美且快速(无论缓冲区长度如何)。

    RC_Server.sendCompleted = false;
    RC_Server.Send(buffer); //in this case buffer size is 1024
    while (!RC_Server.sendCompleted) { } //here thread is waiting for the send to complete

现在，如果我想开始与服务器的接收 session

        RC_Server.receiveCompleted = false;
        RC_Server.Receive(buffer.Length); //in this case byffer needs to get 4 bytes from server
        while (!RC_Server.receiveCompleted) { } // <<- Here it will take VERY long time for the operation to complete
        buffer = RC_Server.buffer;

第二个接收操作永远不会到达socket_receiveCompleted_Completed事件。

但是..如果我将在第一个发送/接收 session 后关闭与服务器的连接，然后打开与服务器的新连接，然后执行下一个发送/接收 session ，
那么一切都会完美地进行。 (并多次重复此方法以进行多次发送/接收)

再次，在我的工作站中不会发生此问题(如果我在同一台PC上运行服务器和客户端)。仅当我将服务器托管在远程主机上时，它才会发生。

这是我的套接字类的一部分:

    class SocketConnection_Client
    {
        public string errorMsg = string.Empty;
        public bool receiveCompleted = false;
        public bool sendCompleted = false;
        int bytesReceived = 0;
        public byte[] buffer;
        Socket socket;

        public SocketConnection_Client(IPEndPoint ipEP)
        {
            socket = new Socket(ipEP.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
            try
            {
                socket.Connect(ipEP);
            }
            catch (Exception ex)
            {
                errorMsg = ex.Message;
                socket.Dispose();
                socket = null;
            }
        }

        public void Send(byte[] sBuffer)
        {
            buffer = null;
            if (socket == null)
            {
                sendCompleted = true;
                return;
            }
            sendCompleted = false;

            SocketAsyncEventArgs socket_sendCompleted = new SocketAsyncEventArgs();
            socket_sendCompleted.SetBuffer(sBuffer, 0, sBuffer.Length);
            socket_sendCompleted.Completed += socket_sendCompleted_Completed;
            socket.SendAsync(socket_sendCompleted);
        }

        void socket_sendCompleted_Completed(object sender, SocketAsyncEventArgs e)
        {
            sendCompleted = true;
        }

        public void Receive(int bLength)
        {
            bytesReceived = 0;
            buffer = null;
            if (socket == null)
            {
                receiveCompleted = true;
                return;
            }
            receiveCompleted = false;

            buffer = new byte[bLength];
            SocketAsyncEventArgs socket_receiveCompleted = new SocketAsyncEventArgs();
            socket_receiveCompleted.SetBuffer(buffer, 0, buffer.Length);
            socket_receiveCompleted.Completed += socket_receiveCompleted_Completed;
            socket.ReceiveAsync(socket_receiveCompleted);
        }

        private void Receive_Continue()
        {
            SocketAsyncEventArgs socket_receiveCompleted = new SocketAsyncEventArgs();
            socket_receiveCompleted.SetBuffer(buffer, bytesReceived, buffer.Length - bytesReceived);
            socket_receiveCompleted.Completed += socket_receiveCompleted_Completed;
            socket.ReceiveAsync(socket_receiveCompleted);
        }

        void socket_receiveCompleted_Completed(object sender, SocketAsyncEventArgs e)
        {
            bytesReceived += e.BytesTransferred;
            if (e.BytesTransferred == 0 && bytesReceived == 0)
            {
                socket.Dispose();
                socket = null;
                receiveCompleted = true;
                throw new Exception("Server Disconnected");
            }
            else if (bytesReceived != buffer.Length)
                Receive_Continue();
            else
                receiveCompleted = true;
        }
    }

感激。
谢谢。

Answer 1

您将忽略ReceiveAsync的返回值。请注意the documentation-有两种可能的行为，您必须检查返回值以区分它们:

Returns true if the I/O operation is pending. The SocketAsyncEventArgs.Completed event on the e parameter will be raised upon completion of the operation.

Returns false if the I/O operation completed synchronously. In this case, the SocketAsyncEventArgs.Completed event on the e parameter will not be raised and the e object passed as a parameter may be examined immediately after the method call returns to retrieve the result of the operation.