UDP协议。

看代码：

服务端：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;

namespace UDPServer
{
        class Program
        {
                static void Main(string[] args)
                {
                        int recv;
                        byte[] data = new byte[1024];

                        //构建TCP 服务器

                        //得到本机IP，设置TCP端口号                
                        IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("192.168.1.125"), 8001);
                        Socket newsock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram , ProtocolType.Udp);

                        //绑定网络地址
                        newsock.Bind(ipep);

                        Console.WriteLine("这里是服务器, 主机名是 {0}",Dns.GetHostName());

                        //等待客户机连接
                        Console.WriteLine("等待客户端连接");

                        //得到客户机IP
                        IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
                        EndPoint Remote = (EndPoint)(sender);
                        recv = newsock.ReceiveFrom(data, ref Remote);//会阻塞
                        Console .WriteLine ("消息来自 {0}: ", Remote.ToString ());
                        Console.WriteLine(Encoding.UTF8.GetString(data, 0, recv));

                        //客户机连接成功后，发送欢迎信息
                        string welcome = "欢迎 ! ";

                        //字符串与字节数组相互转换
                        //data    = Encoding .ASCII .GetBytes(welcome);
                        data = Encoding.UTF8.GetBytes("服务端>>>"+welcome);

                        //发送信息
                        newsock.SendTo(data, data.Length, SocketFlags.None, Remote);
                        while (true)
                        {
                                data =new byte [1024];
                                //发送接受信息
                                recv =newsock.ReceiveFrom(data ,ref Remote);
                                Console.Write("客户端>>>");
                                Console.WriteLine(Encoding.UTF8.GetString(data, 0, recv));

                                //向客户端回复信息
                                newsock.SendTo(data,recv,SocketFlags.None, Remote);
                        }
                }
        }
}


客户端:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net;
using System.Net.Sockets;

namespace UdpClient
{
        class Program
        {
                static void Main(string[] args)
                {
                        byte[] data = new byte[1024];
                        string input, stringData;


                        Console.WriteLine("这里是客户端, 主机名是 {0}", Dns.GetHostName());

                        //设置服务端IP，设置TCP端口号
                        IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("192.168.1.125"), 8001);

                        //定义网络类型，数据连接类型和网络协议UDP
                        Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

                        string welcome = "你好! ";
                        data = Encoding.UTF8.GetBytes("客户端>>>" + welcome);
                        server.SendTo(data, data.Length, SocketFlags.None, ipep);//向服务端发送数据

                        IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
                        EndPoint Remote = (EndPoint)sender;

                        data = new byte[1024];
                        //对于不存在的IP地址，加入此行代码后，可以在指定时间内解除阻塞模式限制
                        //server.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 100);
                        int recv = server.ReceiveFrom(data, ref Remote);//将数据接收放入缓冲区
                        Console.WriteLine("消息来自服务端 {0}: ", Remote.ToString());
                        Console.WriteLine(Encoding.UTF8.GetString(data, 0, recv));

                        while (true)
                        {
                                input = Console.ReadLine();

                                //如果输入exit则退出
                                if (input == "exit" || input=="quit")
                                        break;

                                //input = "客户端>>>" + input;
                                server.SendTo(Encoding.UTF8.GetBytes(input), Remote);

                                data = new byte[1024];
                                recv = server.ReceiveFrom(data, ref Remote);
                                stringData = Encoding.UTF8.GetString(data, 0, recv);
                                Console.Write("服务端回复>>>");
                                Console.WriteLine(stringData);
                        }
                        Console.WriteLine("客户端关闭.");
                        server.Close();
                }
        }
}

研究一个教程，只做了些改动。