import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;


public class UDPCilent {

	public static void main(String[] args) {
		try {
			/*
			 * 向服务器端发送信息
			 */
			//定义服务器ip，端口，信息
			InetAddress address=InetAddress.getByName("localhost");
			int port=8000;
			byte []data="用户名：kuerban;密码：668858".getBytes();
			//建立DatagramPacket
			DatagramPacket packet=new DatagramPacket(data, 0, data.length, address, port);
			//建立DatagramSocket
			DatagramSocket socket=new DatagramSocket();
			socket.send(packet);
			
			/*
			 * 获取服务端发送信息
			 */
			//建立数据包接受信息
			byte bytes[]=new byte[1024];
			DatagramPacket packet1=new DatagramPacket(bytes, bytes.length);
			socket.receive(packet1);
			String info=new String(bytes, 0, packet1.getLength());
			System.out.println(info);
			socket.close();
		} catch (UnknownHostException | SocketException e) {
			e.printStackTrace();
		} catch (IOException e) {			
			e.printStackTrace();
		}
	}
	

}


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

/*
 * 服务器端，基于UDP实现用户登录
 */



public class UDPServer {

	public static void main(String[] args) {
		try {
		/*
		 * 接受信息
		 */
			
			//建立一个DatagramSocket,指定端口
			DatagramSocket socket=new DatagramSocket(8000);
			byte []bytes=new byte[1024];
			//建立一个Datagrampacket，以接受数据
			DatagramPacket packet=new DatagramPacket(bytes, bytes.length);
		/*
		 * 发送数据
		 */		
			//启动服务器
			System.out.println("服务器已启动");
			while(true){
			    socket.receive(packet);
			    //建立客户端ip，端口
				InetAddress address=packet.getAddress();
				int port=packet.getPort();
				UDPthread thread=new UDPthread(socket,packet,address,port,bytes);
				thread.start();
			}
			
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

}

import java.io.IOException;

import java.net.DatagramPacket;

import java.net.DatagramSocket;

import java.net.InetAddress;

public class UDPthread extends Thread{

DatagramPacket packet=null;

InetAddress address=null;

byte bytes[];

int port=0;

DatagramSocket socket=null;

public UDPthread(DatagramSocket socket,DatagramPacket packet,InetAddress address,int port,byte[] bytes) {

this.packet =packet;

this.address=address;

this.port=port;

this.socket=socket;

this.bytes=bytes;

}

public void run(){

//读取信息,输出信息

String info=new String(bytes, 0, packet.getLength());

System.out.println(info);

//建立信息，并发送

byte bytes1[]="登陆成功".getBytes();

DatagramPacket packet1=new DatagramPacket(bytes1, 0, bytes1.length,address,port);

//向客户端响应

try {

socket.send(packet1);

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}