客户端代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace UDPTest
{
    public partial class Form1 : Form
    {
        private UdpClient udpSend;
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            udpSend = new UdpClient();
            udpSend.EnableBroadcast = true;//是否可以发送和接收广播
            IPEndPoint iep = new IPEndPoint(IPAddress.Parse("224.100.0.10"), 8001);
            byte[] data = Encoding.UTF8.GetBytes(richTextBox1.Text);
            udpSend.Send(data, data.Length, iep);
            richTextBox1.Clear();
        }
    }
}

服务端代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

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

namespace UDPTest2
{
    public partial class Form1 : Form
    {
        
        UdpClient udpReceive;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

        }

        private void Form1_Load(object sender, EventArgs e)
        {
            byte[] data = null;
            udpReceive = new UdpClient(8001);
            udpReceive.JoinMulticastGroup(IPAddress.Parse("224.100.0.10"), 50);//添加到多路广播组，50为路由器跳数
            IPEndPoint iep = new IPEndPoint(IPAddress.Any, 0);
            while (true)
            {
                data = udpReceive.Receive(ref iep);
                string str = Encoding.UTF8.GetString(data, 0, data.Length);
                MessageBox.Show(iep.ToString() + ":" + str);
            }
        }
    }
}