发送方和接收方通信

import java.net.*;
import java.io.*;

class Sender {
    public static void main(String[] args) {
        DatagramPacket dp = null;
        DatagramSocket ds = null;
        try {
            ds = new DatagramSocket(3000);
        } catch(IOException e) {}
        String str = "hello world! ";
        try {
            dp = new DatagramPacket(str.getBytes(),str.length(),InetAddress.getByName("localhost"),9000);
        } catch (UnknownHostException e) {}
        try {
            ds.send(dp);
        } catch(IOException e) {}
        ds.close();
    }
}

class Reciever {
    public static void main(String[] args) {
        DatagramSocket ds = null;
        byte[] buf = new byte[1024];
        DatagramPacket dp = null, dp1 = null;
        try {
            ds = new DatagramSocket(9000);
        } catch(SocketException e) {}
        dp = new DatagramPacket(buf,1024);
        try {
            ds.receive(dp);
        } catch(IOException e) {}
        String str = new String(dp.getData(),0,dp.getLength()) + " from " + dp.getAddress().getHostAddress() + ":" + dp.getPort();
        System.out.println(str);
        String s = "I have received!";
        try {
            dp1 = new DatagramPacket(s.getBytes(),s.length(),InetAddress.getByName("localhost"),3000);
            ds.send(dp1);
        } catch(IOException e) {}
        ds.close();
    }
}