//UDP协议简单实现-----Serverpackage UDP;import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;public class UdpServer implements Runnable {private int port;public UdpServer(int port) {this.port = port;}public void run() {try {// listening at port for udp requestDatagramSocket server = new DatagramSocket(new InetSocketAddress(port));byte[] bs = new byte[4];ByteBuffer bbuf = null;DatagramPacket data = new DatagramPacket(bs, bs.length);server.setSoTimeout(1000 * 10); // set timeoutwhile (true) { // 一直监听
                server.receive(data);bbuf = ByteBuffer.wrap(bs, 0, 4);String s = "receive " + data.getData().length + " byte data,value: " + bbuf.getInt();System.out.println(s);}} catch (Exception e) {e.printStackTrace();}}public static void main(String[] args) {new Thread(new UdpServer(11111)).start();}
}

package UDP;import java.net.DatagramPacket;import java.net.DatagramSocket;import java.net.InetSocketAddress;public class UdpClient implements Runnable {private int port;public UdpClient(int port) {this.port = port;}public void run() {try {DatagramSocket client = new DatagramSocket();byte[] bs = new byte[4];InetSocketAddress isa = new InetSocketAddress("localhost", port);DatagramPacket data = new DatagramPacket(bs, bs.length);data.setSocketAddress(isa);for (int i = 0; i < 10; i++) {data.setData(int2bytes(i));client.send(data);}} catch (Exception e) {e.printStackTrace();}}static byte[] int2bytes(int num) {byte[] b = new byte[4];for (int i = 0; i < 4; i++) {b[i] = (byte) (num >>> (24 - i * 8));}return b;}}

package UDP;public class Test {public static void main(String[] args) throws InterruptedException {int port = 11111;try{new Thread(new UdpServer(port)).start();new Thread(new UdpClient(port)).start();}catch(Exception e){//e.printStackTrace();
        }}
}