本文转载自：http://blog.csdn.net/wanlong360599336/article/details/7557046

先看效果图：

使用UDP的好处就是不需要三次握手，但是缺点就是存在安全隐患。

QQ就是利用UDP来传输数据的。

 

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.Sockets;  using System.Threading;  using System.Net;  using System.Net.Sockets;    namespace UDP  {      public partial class Form1 : Form      {          public Form1()          {              InitializeComponent();          }          //启动服务端          UdpClient udpServer;          delegate void SetTextCallBack(string text);          private void button1_Click(object sender, EventArgs e)          {              udpServer = new UdpClient(3000);              label2.Text = "服务器已启动..";              button1.Enabled = false;              Thread t = new Thread(new ThreadStart(ReceiveMsg));              t.IsBackground = true;              t.Start();                        }                    public void ReceiveMsg()          {              IPEndPoint ipe = new IPEndPoint(IPAddress.Any, 3000);              while (true)              {                              byte[] buffer = udpServer.Receive(ref ipe);                  string msg = Encoding.Unicode.GetString(buffer);                      SetText(msg);              }                        }          public void SetText(string text)          {              if (text == "")              {                  if (richTextBox1.InvokeRequired)                  {                      SetTextCallBack st = new SetTextCallBack(SetText);                      this.Invoke(st, new object[] { text });                  }                  else                  {                      richTextBox1.Text +="小万  " +DateTime.Now.ToString() + "\n" + " " + "\n";                  }              }              else              {                                        if (richTextBox1.InvokeRequired)                      {                          SetTextCallBack st = new SetTextCallBack(SetText);                          this.Invoke(st, new object[] { text });                      }                      else                      {                          richTextBox1.Text +="小万  " +DateTime.Now.ToString() + "\n" + text  + "\n";                      }                                }          }          //客户端          private void button2_Click(object sender, EventArgs e)          {              if (button1.Enabled ==true)              {                  MessageBox.Show("服务端未开启！");              }              else              {                  UdpClient client = new UdpClient();                  string ip = textBox1.Text;                  string msg = richTextBox2.Text;                  byte[] buffer = Encoding.Unicode.GetBytes(msg);                  IPEndPoint ips = new IPEndPoint(IPAddress.Parse(ip), 3000);                  client.Send(buffer, buffer.Length, ips);                  client.Close();                  MessageBox.Show("发送成功！");              }            }             }  }

自己理解下。