基于UDP协议的网络编程

       UDP协议是一种不可靠的网络协议，它在通信实例的两端各机建立一个Socket，但这两个Socket之间并没有虚拟链路，这两个Socket只是发送、接收数据报的对象，Java提供了DatagramSocket对象作为基于UDP协议的Socket，使用DatagramPacket代表DatagramSocket发送、接收的数据报.

send()发送数据报。

receive()接收数据报。

package com.net.udp;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.SocketException;public class UdpServer {public static final int port=30000;//定义每个数据包的大小为4kprivate static int DATA_LEN=4096;//定义该服务器使用的DatagramSocketprivate DatagramSocket socket=null;//定义接收网路数据的字节数组byte[] inBuff=new byte[DATA_LEN];//以指定字节数组创建准备接受数据的DatagramPacket对象private DatagramPacket inPacket=new DatagramPacket(inBuff, inBuff.length);//定义一个用于发送的DatagramPacket对象private DatagramPacket outPacket;//定义一个字符串数组，服务器发送该数组的元素String[] books=new String[]{"美丽说","绝世武神","莽荒纪","帅哥","美女"};public void init(){try {//创建DatagramSocket对象socket=new DatagramSocket(port);//采用循环接收数据for(int i=0;i<1000;i++){socket.receive(inPacket);//判断inPacket.getData()和inBuff是否是同一个数组System.out.println(inPacket.getData()==inBuff);//将接收到的内容转换成字符串后输出System.out.println(new String(inBuff,0,inPacket.getLength()));//从字符串数组中取出一个元素作为发送的数据byte[] sendData=books[i%4].getBytes();//以指定字节数组作为发送数据、以刚接收到的DatagarmPacket的源SocketAddress作为目标SocketAddress创建DatagramPacketoutPacket=new DatagramPacket(sendData, sendData.length, inPacket.getSocketAddress());//发送数据socket.send(outPacket);}} catch (SocketException e) {e.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{if(socket!=null){socket.close();}}}public static void main(String[] args) {new UdpServer().init();}}

package com.net.udp;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetAddress;import java.net.SocketException;import java.net.UnknownHostException;import java.util.Scanner;public class UdpClient {public static final int DEST_PORT=30000;public static final String DEST_IP="127.0.0.1";//定义每个数据报的最大发小为4k private static final int DATA_LEN=4096; //定义该客户端使用的DatagramSocket private DatagramSocket socket=null; //定义接收网路数据的字节数组 byte[] inBuff=new byte[DATA_LEN];//以指定字节数组创建准备接受数据的DatagramPacket对象 private DatagramPacket inPacket=new DatagramPacket(inBuff, inBuff.length); //定义一个用于发送的DatagramPacket对象 private DatagramPacket outPacket=null;  public void init(){ try {//创建一个客户端DatagramSocket，使用随机端口 socket=new DatagramSocket();outPacket=new DatagramPacket(new byte[0], 0,InetAddress.getByName(DEST_IP),DEST_PORT);//创建键盘输入流Scanner scan=new Scanner(System.in);//不断读取键盘输入while(scan.hasNextLine()){byte[] buff=scan.nextLine().getBytes();//设置发送用的DatagramPacket里的字节数据outPacket.setData(buff);//发送数据报socket.send(outPacket);//读取socket的数据，读到的数据放在inPacket所封装字节数组里socket.receive(inPacket);System.out.println(new String(inBuff,0,inPacket.getLength()));}} catch (SocketException e) {e.printStackTrace();} catch (UnknownHostException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{if(socket!=null){socket.close();}} }public static void main(String[] args) {new UdpClient().init();}}

先运行UdpServer ，再运行UdpClient