package udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.util.UUID;

/**

• UDP 提供者，用于提供服务
  */
  public class UDPProvider {

  public static void main(String args[]) throws IOException {

   String sn = UUID.randomUUID().toString();
   Provider provider = new Provider(sn);
   provider.run();
  
   //读取任意字符退出
   System.in.read();
   provider.exit();
  

  }

  private static class Provider extends Thread{

   private String sn;
   private boolean done = false;
   private DatagramSocket ds = null;
   public Provider(String sn) {
       super();
       this.sn = sn;
   }
  
   @Override
   public void run() {
       super.run();
       System.out.println("UDPProvider started.");
       try{
           ds = new DatagramSocket(20000);
           while(!done){
               //构建接收实体
               byte buf[] = new byte[512];
               final DatagramPacket receivePacket = new DatagramPacket(buf,buf.length);
               //接收
               ds.receive(receivePacket);
               //打印接收到的信息
               String IP = receivePacket.getAddress().getHostAddress();
               int PORT = receivePacket.getPort();
               int length = receivePacket.getLength();
               String data = new String(receivePacket.getData(),0,length);
               System.out.println("UDPProvider 接收到 ip: "+IP+"\tport:"+PORT+"\tLength"+length+"\tDATA"+data);
  
               int port = MessageCreator.parsePort(data);
               if(port!=-1){
                   String sendMessage = MessageCreator.buildWithPort(port);
                   byte[] udpProviderSendByte = sendMessage.getBytes();
                   DatagramPacket sendGramPacket = new DatagramPacket(udpProviderSendByte,0,udpProviderSendByte.length,
                           receivePacket.getAddress(),PORT);
                   ds.send(sendGramPacket);
               }
           }
       }catch (Exception e){
       }finally {
           exit();
       }
   }
  
  
   public void exit(){
       done = true;
       if(ds!=null){
           System.out.println(ds.getInetAddress().getHostAddress()+"\t连接断开！");
           ds.close();
           ds = null;
       }
   }
  

  }
  }

package udp;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;

public class UDPSearcher {

private static final int LISTENPORT = 30000;
public static void main(String args[]) throws Exception {
    Listener listener = listen();
    sendBroadcast();
    System.in.read();
    List<Device> devices = listener.getDeviceAndClose();
    for(Device device:devices ){
        System.out.println(device.toString());
    }
}

private static Listener listen() throws InterruptedException {
    System.out.println("UDPSearcher start!");
    CountDownLatch countDownLatch = new CountDownLatch(1);

    Listener listener = new Listener(LISTENPORT,countDownLatch);
    listener.start();
    countDownLatch.await();
    return listener;
}


private static class Device{
    final int port;
    final String ip;
    final String sn;

    private Device(int port, String ip, String sn) {
        this.port = port;
        this.ip = ip;
        this.sn = sn;
    }

    @Override
    public String toString() {
        return "Device{" +
                "port=" + port +
                ", ip='" + ip + '\'' +
                ", sn='" + sn + '\'' +
                '}';
    }
}


private static class Listener extends Thread {
    private final int listenPort;
    private final CountDownLatch countDownLatch;
    private final List<Device> devices = new ArrayList<>();
    private boolean done = false;
    private DatagramSocket ds  = null;

    public Listener(int listenPort, CountDownLatch countDownLatch) {
        this.listenPort = listenPort;
        this.countDownLatch = countDownLatch;
    }

    @Override
    public void run() {
        super.run();
        countDownLatch.countDown();
        try{
            ds = new DatagramSocket(listenPort);

            while (!done){
                byte buf[] = new byte[512];
                final DatagramPacket receivePacket = new DatagramPacket(buf,buf.length);
                //接收
                ds.receive(receivePacket);
                byte data[]= receivePacket.getData();
                String receivesStr = new String(data,data.length);
                String IP = receivePacket.getAddress().getHostAddress();
                int PORT = receivePacket.getPort();
                System.out.println("searcherSocket 接收到 ip: "+IP+"\tport:"+PORT+"\tLength"+data.length+"\tDATA"+receivesStr);
                String SN = MessageCreator.parseSN(receivesStr);
                if(SN!=null){
                    Device d  = new Device(PORT,IP,SN);
                    devices.add(d);
                }
            }
            System.out.println("UDPSearcher finish!");

        }catch (Exception e){

        }finally {
            close();
        }
    }
    private void close(){
        done = true;
        if(ds!=null){
            ds.close();
            ds = null;
        }
    }
    private List<Device> getDeviceAndClose(){
        close();
        return devices;
    }
}

public static void sendBroadcast() throws Exception {
    System.out.println("UDPSearcher sendBroadcast started.");
    DatagramSocket searcherSocket = new DatagramSocket();
    String sendStr = MessageCreator.buildWithPort(LISTENPORT);

    final DatagramPacket searcherPacket = new DatagramPacket(sendStr.getBytes(),sendStr.getBytes().length);
    searcherPacket.setAddress(InetAddress.getByName("255.255.255.255"));
    searcherPacket.setPort(20000);
    searcherSocket.send(searcherPacket);
    searcherSocket.close();
    System.out.println("UDPSearcher sendBroadcast finish.");

}

}