c# - 如何修复错误 "Only one usage of each socket address (protocol/network address/port) is normally permitted"？

Question

我已经进行了大量的谷歌搜索，但我的问题并没有太多运气。我是网络编程的新手并正在尝试学习，我试图建立一个简单的服务器和客户端进行通信(遵循位于此处的在线教程 -> http://tech.pro/tutorial/704/csharp-tutorial-simple-threaded-tcp-server )

我遇到的问题是，当尝试在服务器上启动 TcpListener 时，我不断收到异常“通常只允许使用每个套接字地址(协议(protocol)/网络地址/端口)一次”。

我试过禁用防火墙、更改要使用的端口、移动变量但无济于事(客户端工作正常，但显然找不到服务器，因为我无法启动它)。

我看过描述 Socket.Poll() 使用的解决方案，但由于我只使用 TcpListener 对象，所以我不知道如何使用 Poll 函数。

我的代码:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using System.Net;
using System.Threading;
using System.Text;

namespace ServerTutorial {
class Server {
    private readonly Thread m_listenThread;

    public Server() {
        m_listenThread = new Thread(new ThreadStart(ListenForClients));
        m_listenThread.Start();
    }

    public void ListenForClients() {
        var listener = new TcpListener(IPAddress.Any, 3000);
        listener.Start();

        while (true) {
            //Blocks until a client has connected to the server
            TcpClient client = listener.AcceptTcpClient();

            //Send a message to the client
            var encoder = new ASCIIEncoding();
            NetworkStream clientStream = client.GetStream();
            byte[] buffer = encoder.GetBytes("Hello Client!");
            clientStream.Write(buffer, 0, buffer.Length);
            clientStream.Flush();

            //Create a thread to handle communication with the connected client
            var clientThread = new Thread(new ParameterizedThreadStart(HandleClient));
            clientThread.Start(client);
        }
    }

    private void HandleClient(object clientObj) { //Param thread start can only accept object types, hence the cast
        var client = (TcpClient) clientObj;
        NetworkStream clientStream = client.GetStream();

        var message = new byte[4096];

        while (true) {
            int bytesRead = 0;

            try {
                //Block until a client sends a message
                bytesRead = clientStream.Read(message, 0, 4096);
            } catch {
                //A socket error has occurred
                System.Diagnostics.Debug.WriteLine("A socket error has occured");
                break;
            }

            if (bytesRead == 0) {
                //The client has disconnected from the server
                System.Diagnostics.Debug.WriteLine("A client has disconnected from the server");
                client.Close();
                break;
            }

            //Message has been received
            var encoder = new ASCIIEncoding();
            System.Diagnostics.Debug.WriteLine(encoder.GetString(message, 0, bytesRead));
        }
    }
}
}

在我的主要方法中:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ServerTutorial {
class Program {
    static void Main(string[] args) {
        var server = new Server();
        server.ListenForClients();
    }
}
}

非常感谢任何帮助!

Answer 1

ListenForClients 被调用两次(在两个不同的线程上)- 一次来自构造函数，一次来自 Main 中的显式方法调用。当 TcpListener 的两个实例尝试监听同一个端口时，您会收到该错误。