import java.io.IOException; 
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 

/** 

* 数据报套接字服务端 

* 

* @author leizhimin 2009-12-2 22:09:07 

*/ 
public  class TestUDPServer { 
         public  static  void main(String[] args)  throws IOException { 
                System.out.println( "--------------server端------------"); 
                 byte[] buff =  new  byte[1024]; 
                 //创建一个数据包,用来服务端接收到的数据 
                DatagramPacket dp =  new DatagramPacket(buff, 0, buff.length); 
                 //创建一个绑定本机9999端口的数据报套接字 
                DatagramSocket ds =  new DatagramSocket(9999); 
                 while ( true) { 
                         //阻塞式的接收一个数据包 
                        ds.receive(dp); 
                        System.out.println( new String(buff, 0, buff.length)); 
                } 
        } 
}

package lavasoft.udpsokt; 

import java.io.IOException; 
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 
import java.net.InetSocketAddress; 

/** 

* 数据报套接字客户端 

* 

* @author leizhimin 2009-12-2 22:34:22 

*/ 
public  class TestUDPClient { 
         public  static  void main(String[] args)  throws IOException { 
                System.out.println( "--------------client端------------"); 
                 byte[] buff =  "Hello Server!".getBytes(); 
                 //创建一个数据包，其中指定了发送的目标地 
                DatagramPacket dp =  new DatagramPacket(buff, 0, buff.length,  new InetSocketAddress( "192.168.1.101", 9999)); 
                 //创建一个数据报套接字,绑定到随机可用的端口上 
                DatagramSocket ds =  new DatagramSocket(); 
                 //通过该数据包套接向目标发送数据 
                ds.send(dp); 
                 //关闭套接字 
                ds.close(); 
        } 
}

--------------server端------------ 
Hello Server! 
Hello Server! 
Hello Server!

--------------client端------------ 

Process finished with exit code 0

import java.io.IOException; 
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 

/** 

* 数据报套接字服务端：接收发送消息 

* 

* @author leizhimin 2009-12-2 22:09:07 

*/ 
public  class TestUDPServer { 
         public  static  void main(String[] args)  throws IOException { 
                System.out.println( "--------------server端------------"); 
                 byte[] buff =  new  byte[1024]; 
                 //创建一个数据包,用来服务端接收到的数据 
                DatagramPacket dp =  new DatagramPacket(buff, 0, buff.length); 
                 //创建一个绑定本机9999端口的数据报套接字 
                DatagramSocket ds =  new DatagramSocket(9999); 
                 while ( true) { 
                         //阻塞式的接收一个数据包 
                        ds.receive(dp); 
                         //打印接收的数据 
                        System.out.println( "[" + dp.getAddress().getHostAddress() +  ":" + dp.getPort() +  "]" +  "的消息：" +  new String(buff, 0, buff.length)); 
                        String msg =  "[" + dp.getAddress().getHostAddress() +  ":" + dp.getPort() +  "]" +  "服务端已经收到你的数据包了！"; 
                         //响应客户端，回复一个消息，当然这个端口地址需要从接收到的数据包中获取 
                        DatagramPacket dps =  new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, dp.getSocketAddress()); 
                        ds.send(dps); 
                } 
        } 
}

import java.io.IOException; 
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 
import java.net.InetSocketAddress; 

/** 

* 数据报套接字客户端；发送接收消息 

* 

* @author leizhimin 2009-12-2 22:34:22 

*/ 
public  class TestUDPClient { 
         public  static  void main(String[] args)  throws IOException { 
                System.out.println( "--------------client端------------"); 
                 byte[] buff =  "Hello Server!".getBytes(); 
                 //创建一个数据包，其中指定了发送的目标地 
                DatagramPacket dp =  new DatagramPacket(buff, 0, buff.length,  new InetSocketAddress( "192.168.14.117", 9999)); 
                 //创建一个数据报套接字,绑定到随机可用的端口上 
                DatagramSocket ds =  new DatagramSocket(); 
                 //通过该数据包套接向目标发送数据 
                ds.send(dp); 

                 byte[] buffres =  new  byte[1024]; 
                 //创建一个用来接收服务器反馈的数据包 
                DatagramPacket dbres =  new DatagramPacket(buffres, 0, buffres.length, ds.getLocalAddress(), ds.getLocalPort()); 
                 //接收数据 
                ds.receive(dbres); 
                 //打印接收的数据 
                System.out.println( new String(buffres, 0, buffres.length)); 
                 //关闭套接字 
                ds.close(); 
        } 
}

--------------server端------------ 
[192.168.14.117:4198]的消息：Hello Server!

--------------client端------------ 
[192.168.14.117:4198]服务端已经收到你的数据包了！