import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;


public class FeiQDemo1 {
 
 public static void main(String[] args) throws IOException {
  //第一步： 建立udp的服务
  DatagramSocket socket = new DatagramSocket();
 
  //准备数据，把数据封装到数据包中
  String data = getData("--------------------------------------------------------------------------------------");
  byte[] buf = data.getBytes();
  DatagramPacket packet = new DatagramPacket(buf, buf.length, InetAddress.getByName("192.168.0.255"), 2425);
//广播地址
 
  //调用udp的服务，发送数据
  socket.send(packet);

 
  //关闭资源
  socket.close();
 }
 
 public static String getData(String data){
  StringBuilder sb = new StringBuilder();
  sb.append("1.0:");
  sb.append(System.currentTimeMillis()+":");
  sb.append("非常勿扰:");
  sb.append("192.168.0.9");
  sb.append("32:");
  sb.append(data);
 
  return sb.toString();
 }
}

255为广播地址，学过计算机网络的都知道.
更多网络基础参考
https://blog.csdn.net/mp624183768/article/details/70892015
http://www.cnblogs.com/newwind/category/851282.html