Java 連接MQTT

<dependency>
            <groupId>org.eclipse.paho</groupId>
            <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
            <version>1.2.2</version>
</dependency>

1.模擬客戶端接收消息

import java.util.concurrent.ScheduledExecutorService;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
 
/**
 * 模擬一個客戶端接收消息
 *
 * @author Unclue_liu
 */
public class ClientMQTT {
 
    public static final String HOST = "tcp://192.168.1.77:1883";
    public static final String TOPIC1 = "pos_message_all";
    private static final String clientid = "12345678";
    private MqttClient client;
    private MqttConnectOptions options;
    private String userName = "mqtt";    //非必須
    private String passWord = "mqtt";  //非必須
    private ScheduledExecutorService scheduler;
 
    private void start() {
        try {
            // host爲主機名，clientid即連接MQTT的客戶端ID，一般以唯一標識符表示，MemoryPersistence設置clientid的保存形式，默認爲以內存保存
            client = new MqttClient(HOST, clientid, new MemoryPersistence());
            // MQTT的連接設置
            options = new MqttConnectOptions();
            // 設置是否清空session,這裏如果設置爲false表示服務器會保留客戶端的連接記錄，設置爲true表示每次連接到服務器都以新的身份連接
            options.setCleanSession(false);
            // 設置連接的用戶名
            options.setUserName(userName);
            // 設置連接的密碼
            options.setPassword(passWord.toCharArray());
            // 設置超時時間 單位爲秒
            options.setConnectionTimeout(10);
            // 設置會話心跳時間 單位爲秒 服務器會每隔1.5*20秒的時間向客戶端發送個消息判斷客戶端是否在線，但這個方法並沒有重連的機制
            options.setKeepAliveInterval(20);
            //設置斷開後重新連接
            options.setAutomaticReconnect(true);
            // 設置回調
            client.setCallback(new PushCallback());
            MqttTopic topic = client.getTopic(TOPIC1);
            //setWill方法，如果項目中需要知道客戶端是否掉線可以調用該方法。設置最終端口的通知消息
            //遺囑
            options.setWill(topic, "close".getBytes(), 1, true);
            client.connect(options);
            //訂閱消息
            int[] Qos = {1};//0：最多一次 、1：最少一次 、2：只有一次
            String[] topic1 = {TOPIC1};
            client.subscribe(topic1, Qos);
 
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    public static void main(String[] args)  {
        ClientMQTT client = new ClientMQTT();
        client.start();
 
    }

2.模擬服務端發送消息

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttPersistenceException;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
/**
 * Title:Server 這是發送消息的服務端
 * Description: 服務器向多個客戶端推送主題，即不同客戶端可向服務器訂閱相同主題
 * @author Unclue_liu
 */
public class ServerMQTT {
 
    //tcp://MQTT安裝的服務器地址:MQTT定義的端口號
    public static final String HOST = "tcp://192.168.1.77:1883";
    //定義一個主題
    public static final String TOPIC = "pos_message_all";
    //定義MQTT的ID，可以在MQTT服務配置中指定
    private static final String clientid = "server11";
 
    private MqttClient client;
    private static MqttTopic topic11;
//    private String userName = "mqtt";  //非必須
//    private String passWord = "mqtt";  //非必須
 
    private static MqttMessage message;
 
    /**
     * 構造函數
     * @throws MqttException
     */
    public ServerMQTT() throws MqttException {
        // MemoryPersistence設置clientid的保存形式，默認爲以內存保存
        client = new MqttClient(HOST, clientid, new MemoryPersistence());
        connect();
    }
 
    /**
     *  用來連接服務器
     */
    private void connect() {
        MqttConnectOptions options = new MqttConnectOptions();
        options.setCleanSession(false);
//        options.setUserName(userName);
//        options.setPassword(passWord.toCharArray());
        // 設置超時時間
        options.setConnectionTimeout(10);
        // 設置會話心跳時間
        options.setKeepAliveInterval(20);
        try {
            client.setCallback(new PushCallback());
            client.connect(options);
            topic11 = client.getTopic(TOPIC);
 
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    /**
     *
     * @param topic
     * @param message
     * @throws MqttPersistenceException
     * @throws MqttException
     */
    public static void publish(MqttTopic topic , MqttMessage message) throws MqttPersistenceException,
            MqttException {
        MqttDeliveryToken token = topic.publish(message);
 
        token.waitForCompletion();
        System.out.println("message is published completely! "
                + token.isComplete());
    }
 
 
    public static void sendMessage(String clieId,String msg)throws Exception{
        ServerMQTT server = new ServerMQTT();
        server.message = new MqttMessage();
        server.message.setQos(1);  //保證消息能到達一次
        server.message.setRetained(true);
        String str ="{\"clieId\":\""+clieId+"\",\"mag\":\""+msg+"\"}";
        server.message.setPayload(str.getBytes());
        try{
            publish(server.topic11 , server.message);
            //斷開連接
//            server.client.disconnect();
        }catch (Exception e){
            e.printStackTrace();
        }
 
    }
    /**
     *  啓動入口
     * @param args
     * @throws MqttException
     */
    public static void main(String[] args) throws Exception {
        sendMessage("123444","哈哈");
    }
}

3.發佈消息回調類

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;
 
/**
 * 發佈消息的回調類
 *
 * 必須實現MqttCallback的接口並實現對應的相關接口方法CallBack 類將實現 MqttCallBack。
 * 每個客戶機標識都需要一個回調實例。在此示例中，構造函數傳遞客戶機標識以另存爲實例數據。
 * 在回調中，將它用來標識已經啓動了該回調的哪個實例。
 * 必須在回調類中實現三個方法：
 *
 *  public void messageArrived(MqttTopic topic, MqttMessage message)接收已經預訂的發佈。
 *
 *  public void connectionLost(Throwable cause)在斷開連接時調用。
 *
 *  public void deliveryComplete(MqttDeliveryToken token))
 *  接收到已經發布的 QoS 1 或 QoS 2 消息的傳遞令牌時調用。
 *  由 MqttClient.connect 激活此回調。
 *
 */
public class PushCallback implements MqttCallback {
 
    public void connectionLost(Throwable cause) {
 
        // 連接丟失後，一般在這裏面進行重連
        System.out.println("連接斷開，可以做重連");
    }
 
    public void deliveryComplete(IMqttDeliveryToken token) {
        System.out.println("deliveryComplete---------" + token.isComplete());
    }
 
    public void messageArrived(String topic, MqttMessage message) throws Exception {
        // subscribe後得到的消息會執行到這裏面
        System.out.println("接收消息主題 : " + topic);
        System.out.println("接收消息Qos : " + message.getQos());
        System.out.println("接收消息內容 : " + new String(message.getPayload()));
    }
}