TCP C# 服务器 Python 客户端无法通信

Question

我正在编写一些套接字服务器、客户端应用程序，但我遇到了一个大问题。我的目标是在 C# 中创建一个异步服务器应用程序，并在 python 中创建一个基本客户端应用程序。当我遵循简单的示例时，两个程序都可以工作。但是，当我编写一个异步服务器时，使用从客户端 APP 发送的 read 和 write 处理程序消息，它不起作用。

这是我正在使用的示例服务器代码。

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;

// State object for reading client data asynchronously
public class StateObject
{
// Client  socket.
public Socket workSocket = null;
// Size of receive buffer.
public const int BufferSize = 1024;
// Receive buffer.
public byte[] buffer = new byte[BufferSize];
// Received data string.
public StringBuilder sb = new StringBuilder();
}

public class AsynchronousSocketListener
{
// Thread signal.
public static ManualResetEvent allDone = new ManualResetEvent(false);

public AsynchronousSocketListener()
{
}

public static void StartListening()
{
    // Data buffer for incoming data.
    byte[] bytes = new Byte[1024];

    // Establish the local endpoint for the socket.
    // The DNS name of the computer
    // running the listener is "host.contoso.com".
    IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
    IPAddress ipAddress = ipHostInfo.AddressList[0];
    IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 3333);
    IPEndPoint ipLocal = new IPEndPoint(IPAddress.Any, 3333);
    // Create a TCP/IP socket.
    Socket listener = new Socket(AddressFamily.InterNetwork,
        SocketType.Stream, ProtocolType.Tcp);

    // Bind the socket to the local endpoint and listen for incoming connections.
    try
    {
        listener.Bind(ipLocal);
        listener.Listen(100);

        while (true)
        {
            // Set the event to nonsignaled state.
            allDone.Reset();

            // Start an asynchronous socket to listen for connections.
            Console.WriteLine("Waiting for a connection...");
            listener.BeginAccept(
                new AsyncCallback(AcceptCallback),
                listener);

            // Wait until a connection is made before continuing.
            allDone.WaitOne();
        }

    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }

    Console.WriteLine("\nPress ENTER to continue...");
    Console.Read();

}

public static void AcceptCallback(IAsyncResult ar)
{
    // Signal the main thread to continue.
    allDone.Set();

    // Get the socket that handles the client request.
    Socket listener = (Socket)ar.AsyncState;
    Socket handler = listener.EndAccept(ar);

    // Create the state object.
    StateObject state = new StateObject();
    state.workSocket = handler;
    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), state);
}

public static void ReadCallback(IAsyncResult ar)
{
    String content = String.Empty;

    // Retrieve the state object and the handler socket
    // from the asynchronous state object.
    StateObject state = (StateObject)ar.AsyncState;
    Socket handler = state.workSocket;

    // Read data from the client socket. 
    int bytesRead = handler.EndReceive(ar);
    Console.WriteLine("\n Enters(0)");
    if (bytesRead > 0)
    {
        Console.WriteLine("\n Enters(1)");
        // There  might be more data, so store the data received so far.
        state.sb.Append(Encoding.ASCII.GetString(
            state.buffer, 0, bytesRead));

        // Check for end-of-file tag. If it is not there, read 
        // more data.
        content = state.sb.ToString();
        if (content.IndexOf("<EOF>") > -1)
        {
            // All the data has been read from the 
            // client. Display it on the console.
            Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
                content.Length, content);
            // Echo the data back to the client.
            Send(handler, content);
        }
        else
        {
            Console.WriteLine("\n Detect");
            // Not all data received. Get more.
            handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
            new AsyncCallback(ReadCallback), state);
        }
    }
    Console.WriteLine("\n Enters(1)");

}

private static void Send(Socket handler, String data)
{
    // Convert the string data to byte data using ASCII encoding.
    byte[] byteData = Encoding.ASCII.GetBytes(data);

    // Begin sending the data to the remote device.
    handler.BeginSend(byteData, 0, byteData.Length, 0,
        new AsyncCallback(SendCallback), handler);
}

private static void SendCallback(IAsyncResult ar)
{
    try
    {
        // Retrieve the socket from the state object.
        Socket handler = (Socket)ar.AsyncState;

        // Complete sending the data to the remote device.
        int bytesSent = handler.EndSend(ar);
        Console.WriteLine("Sent {0} bytes to client.", bytesSent);

        handler.Shutdown(SocketShutdown.Both);
        handler.Close();

    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}


public static int Main(String[] args)
{
    StartListening();
    return 0;
}
}

这是一个简单的测试客户端的python代码

import socket

HOST, PORT = "127.0.0.1", 3333
data = "data"
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    sock.connect((HOST, PORT))
    sock.sendall(data)
    print data
finally:
    sock.close()

由于我在服务器的ReadCallback 上插入了一些调试代码，我看到该例程被调用，但它不会将接收到的数据作为消息处理。它似乎没有端点。

我们将不胜感激任何想法或解决方案。

Answer 1

您的ReadCallback 忽略了bytesRead == 0 时的情况，这意味着客户端停止发送数据。如果您的 Python 代码实际上是在没有 "<EOF>" 的情况下发送 "data"，那么您的连接就会被 C# 服务器忘记。

---

关于您的 C# 代码，您可以改进以下几点：

• 使用ManualResetEventSlim，速度更快，不使用操作系统句柄（除非你实际使用WaitHandle属性）

• 您应该在AcceptCallback 中处理来自EndAccept 的异常，在ReadCallback 中处理来自EndReceive 的异常，并可能改进SendCallback 中的异常处理

• 您每次都在ReadCallback 中从StringBuilder 创建一个字符串，这完全违背了使用StringBuilder 的目的；您应该解析从Encoding.ASCII.GetString 获得的每个字符串以依次搜索每个字符<、E、O、F 和>

 

// Add to StateObject
public const string EOF = "<EOF>";
public int eofOffset = -1;
public int searchOffset = 0;

// In ReadCallback
string data = Encoding.ASCII.GetString(state.buffer, 0, bytesRead);
state.sb.Append(data);
int o = state.searchOffset + state.eofOffset + 1;
while (o < state.sb.Length)
{
    if (state.sb[o] != StateObject.EOF[state.eofOffset + 1])
    {
        state.eofOffset = -1;
        state.searchOffset++;
        o = state.searchOffset;
    }
    else
    {
        state.eofOffset++;
        if (state.eofOffset == StateObject.EOF.Length)
        {
            break;
        }
        o++;
    }
}

// Replace this:
//content = state.sb.ToString();
//if (content.IndexOf("<EOF>") > -1)
// with this:
if (state.eofOffset == StateObject.EOF.Length)
{
    // Here is a good place to turn the StringBuilder into a string
    // Perhaps truncate data to send back up to state.searchOffset
    // ...
}

Answer 2

不是C# 的专家，但我认为您对Python 程序有疑问。

try:
    sock.connect((HOST, PORT))
    sock.sendall("data")
    print data
finally:
    sock.close()

您正在尝试打印未定义的data。因此，except 部分将被执行（如果存在）。然后，程序结束，socket 关闭。