作业1

1. 使用UDP协议编写一个网络程序，设置接收端程序的监听端口是8001，发送端发送的数据是“Hello, world”。

package test;import java.io.IOException;import java.net.*;public class client {    public static void main(String[] args) throws Exception {        // TODO Auto-generated method stub        DatagramSocket ds=new DatagramSocket(3000);        String str="Hello World!!";        DatagramPacket dp=new DatagramPacket(str.getBytes(), str.length(),                InetAddress.getByName("localhost"),8001);        System.out.println("发送信息。。。");        ds.send(dp);        ds.close();    }}

package test;import java.io.IOException;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.SocketException;public class server {    public static void main(String[] args) throws Exception {        // TODO Auto-generated method stub            byte [] buf=new byte[1000];            DatagramSocket ds=new DatagramSocket(8001);            DatagramPacket dp=new DatagramPacket(buf, buf.length);            System.out.println("等到接受。。。。");            ds.receive(dp);            String str=new String(dp.getData(), 0, dp.getLength())+"from"+            dp.getAddress().getHostAddress()+":"+dp.getPort();            System.out.println(str);            ds.close();    }}