Socket編程 之局域網搜索案列 （廣播局域網信息）

1.服務端代碼：

package com.jidongcloud.bean;

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

/**
 * ClassName:CTRL+ALT+L是格式對齊。
 * PackageName:com.jidongcloud.bean
 * Description:  socket 之局域網搜索案列   （廣播局域網信息）     ----提供者
 * 優秀博文  :  https://blog.csdn.net/nicolelili1/article/details/103956181?utm_medium=distribute.pc_relevant.none-task-blog-baidujs-2
 *
 * @date:2020/5/15 17:21
 * @author:robin
 */
public class UDPBroadcastProvider {
    public static void main(String[] args) throws IOException {
        // 生成一份唯一標識
        String sn = UUID.randomUUID().toString();
        Provider provider = new Provider(sn);
        provider.start();
        // 讀取任意鍵盤信息後可以退出
        //noinspection ResultOfMethodCallIgnored
        System.in.read();
        provider.exit();
    }

    private static class Provider extends Thread {
        private final 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 {
                // 監聽20000 端口
                ds = new DatagramSocket(20000);
                while (!done) {
                    // 構建接收實體
                    final byte[] buf = new byte[512];
                    DatagramPacket receivePack = new DatagramPacket(buf, buf.length);
                    // 接收 ,這裏會一直出現阻塞現象，那麼當什麼時候結束呢？ ds=null時候，這時候會走try-catch異常，結束線程。
                      ds.receive(receivePack);
                    // 打印接收到的信息與發送者的信息
                    // 發送者的IP地址
                    String ip = receivePack.getAddress().getHostAddress();
                    int port = receivePack.getPort();
                    int dataLen = receivePack.getLength();
                    String data = new String(receivePack.getData(), 0, dataLen);

                    ////這行代碼在啓動provider時候應該輸出內容
                    System.out.println("UDPProvider receive form ip:" + ip + "\tport:" + port + "\tdata:" + data);
                    // 解析端口號
                    int responsePort = MessageCreator.parsePort(data);
                    if (responsePort != -1) {
                        // 構建一份回送數據
                        String responseData = MessageCreator.buildWithSn(sn);
                        byte[] responseDataBytes = responseData.getBytes();
                        // 直接根據發送者構建一份回送信息
                        DatagramPacket responsePacket = new DatagramPacket(responseDataBytes,
                                responseDataBytes.length, receivePack.getAddress(), responsePort);
                        ds.send(responsePacket);
                    }
                }
            } catch (Exception ignored) {
            } finally {
                close();
            }
            // 完成
            System.out.println("UDPProvider Finished.");
        }

        private void close() {
            if (ds != null) {
                ds.close();
                ds = null;
            }
        }


        /**
         *   提供結束
         *         
         */
        void exit() {
            done = true;
            close();
        }
    }
}

2.客戶端代碼

package com.jidongcloud.bean;

import java.io.IOException;
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;

/**
 * ClassName:UDPBroadcastSearcher
 * PackageName:com.jidongcloud.bean
 * Description:            ----搜尋者
 *
 * @date:2020/5/15 23:23
 * @author:robin
 */
public class UDPBroadcastSearcher {

    /**
     *  * UDP 搜索者，用於搜索服務支持方
     *  
     */

    private static final int LISTEN_PORT = 30000;

    public static void main(String[] args) throws IOException, InterruptedException {
        System.out.println("UDPSearcher Started.");
        Listener listener = listen();
        sendBroadcast();

        // 讀取任意鍵盤信息後可以退出
//noinspection ResultOfMethodCallIgnored
        System.in.read();

        List<Device> devices = listener.getDevicesAndClose();

        for (Device device : devices) {
            System.out.println("Device:" + device.toString());
        }

// 完成
        System.out.println("UDPSearcher Finished.");
    }

    private static Listener listen() throws InterruptedException {
        System.out.println("UDPSearcher start listen.");
        CountDownLatch countDownLatch = new CountDownLatch(1);
        Listener listener = new Listener(LISTEN_PORT, countDownLatch);
        listener.start();
        countDownLatch.await();
        return listener;
    }

    private static void sendBroadcast() throws IOException {
        System.out.println("UDPSearcher sendBroadcast started.");

        // 作爲搜索方，讓系統自動分配端口
        DatagramSocket ds = new DatagramSocket();


// 構建一份請求數據
        String requestData = MessageCreator.buildWithPort(LISTEN_PORT);
        byte[] requestDataBytes = requestData.getBytes();
// 直接構建packet
        DatagramPacket requestPacket = new DatagramPacket(requestDataBytes,
                requestDataBytes.length);
// 20000端口, 廣播地址
        requestPacket.setAddress(InetAddress.getByName("255.255.255.255"));
        requestPacket.setPort(20000);

        // 發送
        ds.send(requestPacket);
        ds.close();

        // 完成
        System.out.println("UDPSearcher sendBroadcast finished.");
    }

    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) {
            super();
            this.listenPort = listenPort;
            this.countDownLatch = countDownLatch;
        }

        @Override
        public void run() {
            super.run();
            // 通知已啓動
            countDownLatch.countDown();
            try {
// 監聽回送端口
                ds = new DatagramSocket(listenPort);


                while (!done) {
// 構建接收實體
                    final byte[] buf = new byte[512];
                    DatagramPacket receivePack = new DatagramPacket(buf, buf.length);

                    // 接收
                    ds.receive(receivePack);

                    // 打印接收到的信息與發送者的信息
// 發送者的IP地址
                    String ip = receivePack.getAddress().getHostAddress();
                    int port = receivePack.getPort();
                    int dataLen = receivePack.getLength();
                    String data = new String(receivePack.getData(), 0, dataLen);
                    System.out.println("UDPSearcher receive form ip:" + ip + "\tport:" + port + "\tdata:" + data);
                    String sn = MessageCreator.parseSn(data);
                    if (sn != null) {
                        Device device = new Device(port, ip, sn);
                        devices.add(device);
                    }
                }
            } catch (Exception ignored) {
            } finally {
                close();
            }
            System.out.println("UDPSearcher listener finished.");

        }

        private void close() {
            if (ds != null) {
                ds.close();
                ds = null;
            }
        }

        List<Device> getDevicesAndClose() {
            done = true;
            close();
            return devices;
        }
    }
}

3.測試信息

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