C# 用Socket写一个点对点通信，要求客户端既是服务端又是服务端，界面上有连接按钮，断开按钮，发送按钮，两个RichTextBox控件,

以下是基于C#的Socket编写点对点通信的代码，客户端既是服务端又是服务端，具有连接、断开、发送等功能，界面上有连接按钮、断开按钮、发送按钮和两个RichTextBox控件：

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

namespace P2PCommunicate
{
    public partial class Form1 : Form
    {
        private Socket _serverSocket; // 服务端Socket
        private Socket _clientSocket; // 客户端Socket
        private Thread _serverThread; // 服务端线程
        private Thread _clientThread; // 客户端线程
        private bool _isServerStarted; // 服务端是否已启动
        private bool _isClientStarted; // 客户端是否已启动
        private string _serverIp = "127.0.0.1"; // 服务端IP地址
        private int _serverPort = 8888; // 服务端端口号
        private string _clientIp = "127.0.0.1"; // 客户端IP地址
        private int _clientPort = 8889; // 客户端端口号

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            UpdateUI(true);
        }

        private void btnConnect_Click(object sender, EventArgs e)
        {
            if (!_isClientStarted)
            {
                _clientThread = new Thread(ClientThreadFunc);
                _clientThread.Start();
            }
            else
            {
                MessageBox.Show("客户端已经连接！", "提示");
            }
        }

        private void btnDisconnect_Click(object sender, EventArgs e)
        {
            if (_isClientStarted)
            {
                _clientSocket.Close();
                _clientThread.Abort();
                _isClientStarted = false;
                UpdateUI(false);
            }
            else
            {
                MessageBox.Show("客户端未连接！", "提示");
            }
        }

        private void btnSend_Click(object sender, EventArgs e)
        {
            if (_isClientStarted)
            {
                SendMessage(txtSend.Text);
                txtSend.Clear();
            }
            else
            {
                MessageBox.Show("客户端未连接！", "提示");
            }
        }

        private void ServerThreadFunc()
        {
            try
            {
                _serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                _serverSocket.Bind(new IPEndPoint(IPAddress.Parse(_serverIp), _serverPort));
                _serverSocket.Listen(10);
                while (true)
                {
                    Socket client = _serverSocket.Accept();
                    Thread receiveThread = new Thread(ReceiveThreadFunc);
                    receiveThread.Start(client);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("服务端异常：" + ex.Message, "错误");
            }
        }

        private void ClientThreadFunc()
        {
            try
            {
                _clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                _clientSocket.Connect(new IPEndPoint(IPAddress.Parse(_clientIp), _clientPort));
                Thread receiveThread = new Thread(ReceiveThreadFunc);
                receiveThread.Start(_clientSocket);
                _isClientStarted = true;
                UpdateUI(true);
            }
            catch (Exception ex)
            {
                MessageBox.Show("客户端异常：" + ex.Message, "错误");
            }
        }

        private void ReceiveThreadFunc(object obj)
        {
            Socket socket = obj as Socket;
            byte[] buffer = new byte[1024];
            while (true)
            {
                int length = socket.Receive(buffer);
                string message = Encoding.UTF8.GetString(buffer, 0, length);
                AppendText(txtReceive, string.Format("[{0:HH:mm:ss}] {1}", DateTime.Now, message));
            }
        }

        private void SendMessage(string message)
        {
            byte[] buffer = Encoding.UTF8.GetBytes(message);
            _clientSocket.Send(buffer);
            AppendText(txtReceive, string.Format("[{0:HH:mm:ss}] {1}", DateTime.Now, message));
        }

        private void AppendText(RichTextBox box, string text)
        {
            if (box.InvokeRequired)
            {
                box.Invoke(new Action<RichTextBox, string>(AppendText), box, text);
            }
            else
            {
                box.AppendText(text + Environment.NewLine);
            }
        }

        private void UpdateUI(bool isConnected)
        {
            btnConnect.Enabled = !isConnected;
            btnDisconnect.Enabled = isConnected;
            btnSend.Enabled = isConnected;
            txtSend.Enabled = isConnected;
            txtReceive.Enabled = isConnected;
        }
    }
}

在窗体设计中，需要添加一个连接按钮（btnConnect）、一个断开按钮（btnDisconnect）、一个发送按钮（btnSend）、一个发送文本框（txtSend）、一个接收文本框（txtReceive）和两个标签（lblServer、lblClient）。

注意：该程序中客户端和服务端使用的是不同的端口号，可以根据实际需要进行修改。