C# .NET 4.0/4.5 UDP 发送问题

Question

我正在用 C# 编写一个网络库，最初使用的是 .NET 3.5 Framework。我最近决定切换到 .NET 4.5，但开始遇到发送 UDP 数据包的问题。我遇到的是如果 UDP 数据包发送太快，Socket.SendToAsync方法以 SocketError 结束的 AddressFamilyNotSupported并且永远不会发送数据包。

如果我将项目切换到 .NET 3.5，无论我多么努力地重复它，我都不会遇到这个问题。这也可以在 .NET 4.0 中重现。

这是 link到我放在一起重现这个问题的项目。如果您向“ClientSnd”或“ServerSnd”按钮发送垃圾邮件，您将看到错误发生。将项目切换到 .NET 3.5 并随心所欲地发送垃圾邮件……完全没有问题。

我一直无法找到很多有用的信息搜索这个问题。有任何想法吗？

编辑(从演示问题的示例项目中添加代码):

这是客户端和服务器都发生绑定(bind)的地方:

            byte[] clientBuffer = new byte[32768];
            byte[] serverBuffer = new byte[32768];

            IPEndPoint clientLocalEndPoint = GetLocalIPEndPoint(0, AddressFamily.InterNetwork);
            IPEndPoint serverLocalEndPoint = GetLocalIPEndPoint(6337, AddressFamily.InterNetwork);

            m_ClientSocket.ExclusiveAddressUse = true;
            m_ServerSocket.ExclusiveAddressUse = true;
            m_ClientSocket.Bind(clientLocalEndPoint);
            m_ServerSocket.Bind(serverLocalEndPoint);

            m_ClientSendArgs.RemoteEndPoint = GetRemoteIPEndPoint("127.0.0.1", 6337, AddressFamily.InterNetwork);
            m_ClientRecvArgs.RemoteEndPoint = m_ClientSocket.LocalEndPoint;

            m_ServerSendArgs.RemoteEndPoint = GetRemoteIPEndPoint("127.0.0.1", ((IPEndPoint)m_ClientSocket.LocalEndPoint).Port, AddressFamily.InterNetwork);
            m_ServerRecvArgs.RemoteEndPoint = m_ServerSocket.LocalEndPoint;

            m_ClientSendArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnClientCompletion);
            m_ClientRecvArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnClientCompletion);
            m_ServerSendArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnServerCompletion);
            m_ServerRecvArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnServerCompletion);

            m_ClientRecvArgs.SetBuffer(clientBuffer, 0, clientBuffer.Length);
            m_ServerRecvArgs.SetBuffer(serverBuffer, 0, serverBuffer.Length);

            ClientReceive();
            ServerReceive();

GetRemoteIPEndPoint和 GetLocalIPEndPoint方法:

    private static IPEndPoint GetRemoteIPEndPoint(string address, int port, AddressFamily addressFamily)
    {
        IPAddress[] ipAddresses = null;

        ipAddresses = Dns.GetHostAddresses(address);

        List<IPEndPoint> ipEndPointList = new List<IPEndPoint>();

        for (int i = 0; i < ipAddresses.Length; i++)
        {
            IPAddress ipAddress = ipAddresses[i];

            if (ipAddress.AddressFamily == addressFamily)
            {
                IPEndPoint ipEndPoint = new IPEndPoint(ipAddress, port);

                ipEndPointList.Add(ipEndPoint);
            }
        }

        return ipEndPointList.ToArray()[0];
    }

    private static IPEndPoint GetLocalIPEndPoint(int port, AddressFamily addressFamily)
    {
        IPEndPoint localEndPoint = null;

        switch (addressFamily)
        {
            case AddressFamily.InterNetwork:
                {
                    localEndPoint = new IPEndPoint(IPAddress.Any, port);

                    break;
                }
            case AddressFamily.InterNetworkV6:
                {
                    localEndPoint = new IPEndPoint(IPAddress.IPv6Any, port);

                    break;
                }
        }

        return localEndPoint;
    }

由于无论谁发送数据(客户端或服务器)都会发生这种情况，因此我将重点关注作为发送者的客户端:

点击 ClientSnd按钮:

    private void Button_ClientSnd_Click(object sender, RoutedEventArgs e)
    {
        lock (SyncRoot)
        {
            byte[] buffer = Encoding.ASCII.GetBytes("Hello there.  Just testing.  Nothing to see here.  Move along.");

            m_ClientSendQueue.Enqueue(buffer);

            if (!m_ClientTransmitting)
            {
                m_ClientTransmitting = true;

                ClientSendBuffer();
            }
        }
    }

客户端的发送方法:

    private void ClientSendBuffer()
    {
        lock (SyncRoot)
        {
            if (m_ClientSendQueue.Count > 0)
            {
                byte[] buffer = m_ClientSendQueue.Dequeue();

                m_ClientSendArgs.SetBuffer(buffer, 0, buffer.Length);

                ClientSend();
            }
            else
            {
                m_ClientTransmitting = false;
            }
        }
    }

    private void ClientSend()
    {
        if (!m_ClientSocket.SendToAsync(m_ClientSendArgs))
        {
            OnClientCompletion(this, m_ClientSendArgs);
        }
    }

客户端的完成回调:

    private void OnClientCompletion(object sender, SocketAsyncEventArgs e)
    {
        SocketError socketError = e.SocketError;

        if (socketError != SocketError.Success)
        {
            ClientConsoleWrite("SocketError: {0}\r\n", socketError);
        }

        switch (e.LastOperation)
        {
            case SocketAsyncOperation.SendTo:
                {
                    if (socketError == SocketError.Success)
                    {
                        ClientConsoleWrite("Client message sent!\r\n");
                    }

                    ClientSendBuffer();

                    break;
                }
            case SocketAsyncOperation.ReceiveFrom:
                {
                    int bytesTransferred = e.BytesTransferred;

                    byte[] buffer = new byte[bytesTransferred];

                    Buffer.BlockCopy(e.Buffer, e.Offset, buffer, 0, bytesTransferred);

                    string message = Encoding.ASCII.GetString(buffer);

                    ClientConsoleWrite("Message received: {0}\r\n", message);

                    ClientReceive();

                    break;
                }
        }
    }

Answer 1

我想通了。发生此问题是因为变量 m_ClientSendArgs 上的底层缓冲区不断使用 SetBuffer 更改。 :

byte[] buffer = m_ClientSendQueue.Dequeue();

m_ClientSendArgs.SetBuffer(buffer, 0, buffer.Length);

当我为其分配一个静态缓冲区并使用 Buffer.BlockCopy 时，问题就消失了:

byte[] buffer = m_ClientSendQueue.Dequeue();

Buffer.BlockCopy(buffer, 0, m_ClientSendBuffer, 0, buffer.Length);

m_ClientSendArgs.SetBuffer(0, buffer.Length);

所以我一直在错误地执行它。奇怪的是，这不是 .NET 3.5 上的问题，也不是 .NET 4.0/4.5 上的 TCP 问题。