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 bzu;
import java.net.DatagramPacket; 
import java.net.DatagramSocket; 
import java.net.InetAddress; 
import java.net.SocketException;
public class PersonTest {
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);
    ds.send(dp);
    ds.close();
}
} 
package bzu;
import java.net.DatagramPacket; 
import java.net.DatagramSocket;
public class ServerTest {
public static void main(String[] args)throws Exception {
    // TODO Auto-generated method stub

    byte[] buf = new byte[1024];

    DatagramSocket ds = new DatagramSocket(8001);//定义一个datagramsocket对象，监听的端口8001

    DatagramPacket dp = new DatagramPacket(buf, 1024);//用于接收数据

    System.out.println("等待接受数据");
    ds.receive(dp);
    String str = new String(dp.getData(), 0, dp.getLength())+"from"+dp.getAddress().getHostAddress()+":"+dp.getPort();

    System.out.println(str);
    ds.close();
}
}