C#编程实现TCP Server服务端，监听到连接请求建立一个持续连接，实现数据通讯功能

在C#中，你可以使用`TcpListener`和`Socket`类创建一个基本的TCP服务器，该服务器会持续监听客户端的连接请求，一旦有连接，就保持一个持久的连接并支持双向数据传输。以下是一个简单的例子：

using System;
using System.Net;
using System.Net.Sockets;

class PersistentTcpServer
{
    private TcpListener server;
    private readonly byte[] receiveBuffer = new byte[1024];

    public PersistentTcpServer(int port)
    {
        server = new TcpListener(IPAddress.Any, port);
        server.Start();
    }

    public void Run()
    {
        Console.WriteLine($"Server started on port {server.LocalEndpoint.Port}");

        while (true)
        {
            Console.WriteLine("Waiting for a connection...");
            Socket client = server.AcceptSocket();

            Console.WriteLine($"Connected to: {client.Client.RemoteEndPoint}");

            // 开始一个新的线程处理每个客户端连接
            Thread clientThread = new Thread(HandleClientConnectionAsync);
            clientThread.Start(client);
        }
    }

    private async void HandleClientConnectionAsync(object obj)
    {
        Socket client = (Socket)obj;
        NetworkStream stream = client.GetStream();

        while (true)
        {
            try
            {
                int bytesReceived = await stream.ReadAsync(receiveBuffer, 0, receiveBuffer.Length);
                if (bytesReceived > 0)
                {
                    string receivedData = Encoding.ASCII.GetString(receiveBuffer, 0, bytesReceived);
                    Console.WriteLine($"Received: {receivedData}");

                    // 发送确认信息
                    byte[] response = Encoding.ASCII.GetBytes("Message received");
                    await stream.WriteAsync(response, 0, response.Length);
                }
                else
                {
                    // 客户端断开连接，退出循环
                    break;
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error handling client: {ex.Message}");
                break;
            }
        }

        stream.Close();
        client.Shutdown(SocketShutdown.Both);
        client.Close();
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        var server = new PersistentTcpServer(12345);
        server.Run();
    }
}

在这个示例中，`Run`方法启动服务器并等待连接。每次有新连接时，它会在新的线程中调用`HandleClientConnectionAsync`方法来处理数据收发。`HandleClientConnectionAsync`中，我们通过异步的方式持续从客户端接收数据，然后发送确认信息，直到客户端主动断开连接。