UDPClient端；

import java.net.*;
import java.io.*;
public class TestUDPClient {public static void main(String args[])throws Exception{long n = 10000;ByteArrayOutputStream baos = new ByteArrayOutputStream();DataOutputStream dos = new DataOutputStream(baos);dos.writeLong(n);byte buf[] = baos.toByteArray();DatagramPacket dp = new DatagramPacket(buf,buf.length,new InetSocketAddress("127.0.01",5678));DatagramSocket ds = new DatagramSocket(9999);//本地端口号；ds.send(dp);ds.close();}
}

UDPServer端；

import java.io.*;
import java.net.*;public class TestUDPServer {public static void main(String args[])throws Exception{byte buf[] = new byte[1024];DatagramPacket dp = new DatagramPacket(buf,buf.length);DatagramSocket ds = new DatagramSocket(5678);while(true){ds.receive(dp);ByteArrayInputStream bais = new ByteArrayInputStream(buf);DataInputStream dis = new DataInputStream(bais);System.out.println(dis.readLong());}}
}