c# - 客户端套接字未获取.NET中的响应字节

Question

我正在服务器套接字上创建和发送消息，但没有得到任何响应，我想知道同样的可能原因。以下是我的客户端套接字示例代码

static void Main()
{
    int _DCPport = 9090;
    IPHostEntry ipHostInfo = Dns.GetHostEntry("HostName");
    Console.WriteLine("Got the IP Host Info" , ipHostInfo.ToString ());
    IPAddress ipAddress = ipHostInfo.AddressList[0];
    Console.WriteLine("Got the IP hadress Info");

    //End point of the host where the socket will be connected
    IPEndPoint remoteDAPEndPoint = new IPEndPoint(ipAddress, _DCPport);

    // Create a clientSocket that connects to host
    Socket clientDAP = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    clientDAP.Connect(remoteDAPEndPoint);
    Console.WriteLine("Client socket connected to remote end point");

    #region Input variables
    string requestString = "Hello";
    string responseString = "";

    byte[] requestByte = System.Text.Encoding.UTF8.GetBytes(requestString);
    byte[] responseByte = new byte[1024];

    StringBuilder messageBuilder = new StringBuilder();
    int byteResult = 0;
    #endregion

    try
    {
        //sending the string as bytes over the socket
        Console.WriteLine("Sending the input " + requestString);
        clientDAP.Send(requestByte);
    }
    catch (SocketException eX)
    {

        Console.WriteLine(eX.Message);
    }

    try
    {
        //recieving the response bytes
        byteResult = clientDAP.Receive(responseByte, clientDAP.Available, SocketFlags.None);
        Console.WriteLine("Recieved {0} bytes as response from remote end point" , byteResult);
        if (clientDAP.Connected)
        {
            responseString = Encoding.UTF8.GetString(responseByte);
            messageBuilder.Append(responseString);
        }
    }
    catch (SocketException eX)
    {

        Console.WriteLine(eX.Message);
    }

    clientDAP.Shutdown(SocketShutdown.Both);
    clientDAP.Disconnect(true);


    string sResult = messageBuilder.ToString();
    Console.WriteLine(sResult);


}

我在调用socket.Recieve()时没有收到任何字节，为什么会这样呢？

Answer 1

从 Socket.Send :

There is also no guarantee that the data you send will appear on the network immediately. To increase network efficiency, the underlying system may delay transmission until a significant amount of outgoing data is collected. A successful completion of the Send method means that the underlying system has had room to buffer your data for a network send

这意味着，当您对 Send的调用完成时，数据甚至可能尚未到达服务器。更不用说服务器有时间来处理您的数据并返回响应了。

但是您的代码直接收费以尝试接收服务器的响应。就其本身而言，这并非不合理。如果您指定了缓冲区的大小，则对 Receive 的调用将一直阻塞，直到收到一些数据为止，而不是使用 Available ，如果没有可用数据，它将很高兴地返回 0。因此，您的 Receive调用最多要求 0字节，这就是您要获得的字节数。

所以换这行

byteResult = clientDAP.Receive(responseByte, 1024, SocketFlags.None);

(或者更好的方法是，引入一个常数和/或使用 responseByte.Length或切换到未明确指定所需字节数的重载)