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

namespace udpClient
{
    //udp客户端
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入要发送的内容：");

            UdpClient udpClient = new UdpClient();
            while (true)
            {
                string message = Console.ReadLine();
                //我的电脑是这个ip，你们自己测的时候根据实际情况而定
                udpClient.SendMessage(message, "192.168.1.104", 3333);
            }
        }
    }



public class UdpClient
    {
        Socket udpSocket;
        public UdpClient()
        {
            //创建Socket
            udpSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);//初始化
        }

        /// <summary>
        /// 发送消息
        /// </summary>
        /// <param name="messages">消息内容</param>
        /// <param name="strIp">目标ip</param>
        /// <param name="port">目标端口号</param>
        public int SendMessage(string message, string strIp, int port)
        {
            //发送数据
            EndPoint serverPoint = new IPEndPoint(IPAddress.Parse(strIp), port);

            if (udpSocket == null)
            {
                Console.WriteLine("socket未初始化！");
                return 0;
            }
            else if (serverPoint == null)
            {
                Console.WriteLine("目标ip和端口号不能为空！");
                return 0;
            }
            else if (message == null || string.IsNullOrEmpty(message))
            {
                Console.WriteLine("发送信息不能为空！");
                return 0;
            }

            byte[] data = Encoding.UTF8.GetBytes(message);
            udpSocket.SendTo(data, serverPoint);//发送
            return 1;
        }
    }
}

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

namespace udpServer
{
    //udp服务器
    class Program
    {
        static void Main(string[] args)
        {
            UdpServer udpServer = new UdpServer("192.168.1.104", 3333);
            udpServer.StartReceive();
            Console.ReadLine();
        }
    }



public class UdpServer
    {
        private Socket udpServer;
        public UdpServer(string strIp, int port)
        {
            //创建socket
            udpServer = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            //绑定ip和端口号
            try
            {
                //绑定的ip可能是错误的，要抛出异常
                udpServer.Bind(new IPEndPoint(IPAddress.Parse(strIp), port));
            }
            catch (Exception ex)
            {
                Console.WriteLine("错误信息：" + ex.Message);
                throw ex;
            }
        }

        /// <summary>
        /// 开始接收消息
        /// </summary>
        public int StartReceive()
        {
            if (udpServer.LocalEndPoint == null)
            {
                Console.WriteLine("未绑定自身ip和端口号");
                return 0;
            }

            new Thread(ReceiveMessage) { IsBackground = true }.Start();
            return 1;
        }

        private void ReceiveMessage()
        {
            while (true)
            {
                //接收数据
                EndPoint remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);//j远端ip和端口，这里设定成所有的ip和端口
                byte[] data = new byte[1024];
                int length = udpServer.ReceiveFrom(data, ref remoteEndPoint);//程序运行到这里是会停顿的
                string message = Encoding.UTF8.GetString(data, 0, length);//从索引0开始接收
                Console.WriteLine("发送方ip：" + (remoteEndPoint as IPEndPoint).Address.ToString() +
                    "-------发送方端口：" + (remoteEndPoint as IPEndPoint).Port +
                    "-------消息内容：" + message);
            }
        }
    }
}