SocketException 由于系统缺少足够的缓冲区空间或队列已满，无法对套接字执行操作

Question

这个问题可能出在哪里？

SocketException 由于系统缺少足够的缓冲区空间或队列已满，无法对套接字执行操作

Socket newsock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
IPEndPoint sender = new IPEndPoint(IPAddress.Any, 50509);
EndPoint tmpRemote = (EndPoint)(sender);

newsock.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
newsock.Bind(ipep);

    while (thread_Listen == true && work == true)
        {
            try
            {
                Object state = new Object();
                **>> at this place >>** newsock.BeginReceiveFrom(buffer, 0, buffer.Length, SocketFlags.None, ref tmpRemote, new AsyncCallback(DoReceiveFrom), state);
                Array.Clear(buffer, 0, buffer.Length);
            }
            catch (SocketException ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }

func DoReceiveFrom 的样子

private void DoReceiveFrom(IAsyncResult iar)
{
    try
    {
        Socket recvSock = (Socket)iar.AsyncState;
        EndPoint clientEP = new IPEndPoint(IPAddress.Any, 0);
        int msgLen = recvSock.EndReceiveFrom(iar, ref clientEP);
        byte[] localMsg = GetAndCleanPacket(buffer);
        string[] packet = Encoding.ASCII.GetString(localMsg).Split(new Char[] { '|' });
        if (packet.Length > 0)
        {
            if (packet[0] == "ms")
            {
                // Connect
                if (packet[1] == "c") MSc(ip[0], packet[9], packet, clientEP);
                else if (packet[1] == "s") MSs(ip[0], packet);
                else if (packet[1] == "d") MDc(ip[0], packet);
            }
            else if (packet[0] == "p") ping(clientEP);
            else if (packet[0] == "sList") serverList(clientEP);
            else if (packet[0] == "bi") brGetInfo(packet, clientEP);
            else if (packet[0] == "error") AddError(packet[1], packet[2]);
        }
    }
    catch (InvalidOperationException)
    {
    }
    catch (SocketException)
    {
    }
    catch (Exception e)
    {
        errors.Add(e.ToString());
    }
}

Answer 1

您的 while 循环以非常高的速率调用 BeginReceiveFrom()。在操作系统拔掉插头并拒绝分配更多资源之前，应该不会超过几分之一秒。

您必须以不同的方式执行此操作，仅在您收到某些内容后调用 BeginReceiveFrom。在 DoReceiveFrom() 中。

Answer 2

我所做的是使用包含“IAsyncResult”对象的“StateObject”类。这应该用于 TCP 和 UDP。这是 UDP 的示例。

    // Used for receiver to signal client that data has been received
    // 'readonly' for .Net 4.8
    private readonly ManualResetEvent receiveDone = new ManualResetEvent(false);

    /// <summary>
    /// Supports async receive on UDP socket
    /// </summary>
    private class StateObject
    {
        // Client socket.  
        public UdpClient workSocket = null;
        // Receive buffer.  
        public byte[] buffer;
        // Received data string.  
        public StringBuilder sb = new StringBuilder();
        //public int bytesRead;
        // receiver state
        public IAsyncResult result;

        public delegate void RecvMethod(IAsyncResult result);

        public void BeginReceive(RecvMethod recvMethod, UdpClient udpClient)
        {
            // Set the socket
            workSocket = udpClient;
            // start async receiver
            result = workSocket.BeginReceive(new AsyncCallback(recvMethod), this);
        }
    }

“Receive”方法（由客户端应用调用）检查其状态，并且仅在接收器未发出信号（使用 receiveDone）且 IAsyncResult.Completed 为 false 时触发。

这是这里的关键：如果接收器仍然处于活动状态，请不要再次触发它，否则您会浪费系统资源。它需要另一个套接字和缓冲内存空间，这会占用您的应用程序，通常是在您尝试与离线设备通信时。

    /// <summary>
    /// Set up async receive handler
    /// </summary>
    /// <returns></returns>
    public void Receive()
    {
        // if receiver running, no packet received - do not restart receiver!
        // did receiver signal done?
        if (receiveDone.WaitOne(0))
        {
            // yes - do not restart receiver!
        }
        // is receiver still running?
        else if (CurrentState.result != null && !CurrentState.result.IsCompleted)
        {
            // yes - do not restart receiver!
        }
        else
        {
            // Begin receiving the data from the remote device.
            CurrentState.BeginReceive(ReceiveCallback, udpClient);
        }
    }

接收回调如下所示：

    /// <summary>
    /// End receive (with blocking) and process received data into buffer
    /// </summary>
    /// <param name="ar">Information about the async operation</param>
    private void ReceiveCallback(IAsyncResult ar)
    {
        // Retrieve the state object and the client socket
        // from the asynchronous state object.
        StateObject st = ar.AsyncState as StateObject;
        UdpClient client = st.workSocket;

        try
        {
            st.buffer = client.EndReceive(ar, ref receivePoint);
            // Read data from the remote device.
            receiveDone.Set();
        }
        // Since this is a callback, catch any error
        // ObjectDisposedException has been seen
        catch (ObjectDisposedException)
        { }
        // "An existing connection was forcibly closed by remote host" has been seen
        // see https://stackoverflow.com/questions/38191968/c-sharp-udp-an-existing-connection-was-forcibly-closed-by-the-remote-host for further information
        catch
        {
        }
    }