代码分享：UDP协议聊天工具的编写

using System;  
using System.Collections.Generic;  
using System.ComponentModel;  
using System.Data;  
using System.Drawing;  
using System.Text;  
using System.Windows.Forms;  
using System.Net;  
using System.Net.Sockets;  
using System.Threading;  
namespace MulticastExample  
{  
    public partial class Form1 : Form  
    {  
        delegate void AppendStringCallback(string text);  
        AppendStringCallback appendStringCallback;  
        //使用的接收端口号  
        private int port = 8001;  
        private UdpClient udpClient;  
        public Form1()  
        {  
            InitializeComponent();  
            appendStringCallback = new AppendStringCallback(AppendString);  
        }  
        private void AppendString(string text)  
        {  
            if (richTextBox1.InvokeRequired)  
            {  
                richTextBox1.Invoke(appendStringCallback, text);  
            }  
            else 
            {  
                richTextBox1.AppendText(text + "\r\n");  
            }  
        }  
        private void ReceiveData()  
        {  
            udpClient = new UdpClient(port);  
            //必须使用UDP协议组播的地址范围内的地址  
            udpClient.JoinMulticastGroup(IPAddress.Parse("224.100.0.1"), 50);  
            IPEndPoint remote = null;  
            //接收从远程主机发送过来的信息  
            while (true)  
            {  
                try 
                {  
                    //关闭udpClient时此句会产生异常  
                    byte[] bytes = udpClient.Receive(ref remote);  
                    string str = Encoding.UTF8.GetString(bytes, 0, bytes.Length);  
                    AppendString(string.Format("来自{0}：{1}", remote, str));  
                }  
                catch 
                {  
                    //退出循环，结束线程  
                    break;  
                }  
            }  
        }  
        private void btnSend_Click(object sender, EventArgs e)  
        {  
            UdpClient myUdpClient = new UdpClient();  
            try 
            {  
                //允许发送和接收广播数据报  
                myUdpClient.EnableBroadcast = true;  
                //必须使用组播地址范围内的地址  
                IPEndPoint iep = new IPEndPoint(IPAddress.Parse("224.100.0.1"), port);  
                //将发送内容转换为字节数组  
                byte[] bytes = Encoding.UTF8.GetBytes(txbSend.Text);  
                //向子网发送信息  
                myUdpClient.Send(bytes, bytes.Length, iep);  
                txbSend.Clear();  
                txbSend.Focus();  
            }  
            catch (Exception err)  
            {  
                MessageBox.Show(err.Message, "发送失败");  
            }  
            finally  
            {  
                myUdpClient.Close();  
            }  
        }  
        private void Form1_Load(object sender, EventArgs e)  
        {  
            Thread receiveThread = new Thread(new ThreadStart(ReceiveData));  
            //将线程设为后台运行  
            receiveThread.IsBackground = true;  
            receiveThread.Start();  
        }  
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)  
        {  
            udpClient.Close();  
        }  
    }  
} 
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