Java连接mqtt服务器（发送、订阅）

刺骨的言语ヽ痛彻心扉 2023-10-10 08:28 42阅读 0赞

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

# 1.模拟客户端接收消息 #

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;
    
    /**
     * 模拟一个客户端接收消息
     *
     * @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";    //非必须
        private String passWord = "mqtt";  //非必须
        private ScheduledExecutorService scheduler;
    
        private void start() {
            try {
                // host为主机名，clientid即连接MQTT的客户端ID，一般以唯一标识符表示，MemoryPersistence设置clientid的保存形式，默认为以内存保存
                client = new MqttClient(HOST, clientid, new MemoryPersistence());
                // MQTT的连接设置
                options = new MqttConnectOptions();
                // 设置是否清空session,这里如果设置为false表示服务器会保留客户端的连接记录，设置为true表示每次连接到服务器都以新的身份连接
                options.setCleanSession(false);
                // 设置连接的用户名
                options.setUserName(userName);
                // 设置连接的密码
                options.setPassword(passWord.toCharArray());
                // 设置超时时间 单位为秒
                options.setConnectionTimeout(10);
                // 设置会话心跳时间 单位为秒 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制
                options.setKeepAliveInterval(20);
                //设置断开后重新连接
                options.setAutomaticReconnect(true);
                // 设置回调
                client.setCallback(new PushCallback());
                MqttTopic topic = client.getTopic(TOPIC1);
                //setWill方法，如果项目中需要知道客户端是否掉线可以调用该方法。设置最终端口的通知消息
                //遗嘱
                options.setWill(topic, "close".getBytes(), 1, true);
                client.connect(options);
                //订阅消息
                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.模拟服务端发送消息 #

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 这是发送消息的服务端
     * Description: 服务器向多个客户端推送主题，即不同客户端可向服务器订阅相同主题
     * @author Unclue_liu
     */
    public class ServerMQTT {
    
        //tcp://MQTT安装的服务器地址:MQTT定义的端口号
        public static final String HOST = "tcp://192.168.1.77:1883";
        //定义一个主题
        public static final String TOPIC = "pos_message_all";
        //定义MQTT的ID，可以在MQTT服务配置中指定
        private static final String clientid = "server11";
    
        private MqttClient client;
        private static MqttTopic topic11;
    //    private String userName = "mqtt";  //非必须
    //    private String passWord = "mqtt";  //非必须
    
        private static MqttMessage message;
    
        /**
         * 构造函数
         * @throws MqttException
         */
        public ServerMQTT() throws MqttException {
            // MemoryPersistence设置clientid的保存形式，默认为以内存保存
            client = new MqttClient(HOST, clientid, new MemoryPersistence());
            connect();
        }
    
        /**
         *  用来连接服务器
         */
        private void connect() {
            MqttConnectOptions options = new MqttConnectOptions();
            options.setCleanSession(false);
    //        options.setUserName(userName);
    //        options.setPassword(passWord.toCharArray());
            // 设置超时时间
            options.setConnectionTimeout(10);
            // 设置会话心跳时间
            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);  //保证消息能到达一次
            server.message.setRetained(true);
            String str ="{\"clieId\":\""+clieId+"\",\"mag\":\""+msg+"\"}";
            server.message.setPayload(str.getBytes());
            try{
                publish(server.topic11 , server.message);
                //断开连接
    //            server.client.disconnect();
            }catch (Exception e){
                e.printStackTrace();
            }
    
        }
        /**
         *  启动入口
         * @param args
         * @throws MqttException
         */
        public static void main(String[] args) throws Exception {
            sendMessage("123444","哈哈");
        }
    }

# 3.发布消息回调类 #

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
    import org.eclipse.paho.client.mqttv3.MqttCallback;
    import org.eclipse.paho.client.mqttv3.MqttMessage;
    
    /**
     * 发布消息的回调类
     *
     * 必须实现MqttCallback的接口并实现对应的相关接口方法CallBack 类将实现 MqttCallBack。
     * 每个客户机标识都需要一个回调实例。在此示例中，构造函数传递客户机标识以另存为实例数据。
     * 在回调中，将它用来标识已经启动了该回调的哪个实例。
     * 必须在回调类中实现三个方法：
     *
     *  public void messageArrived(MqttTopic topic, MqttMessage message)接收已经预订的发布。
     *
     *  public void connectionLost(Throwable cause)在断开连接时调用。
     *
     *  public void deliveryComplete(MqttDeliveryToken token))
     *  接收到已经发布的 QoS 1 或 QoS 2 消息的传递令牌时调用。
     *  由 MqttClient.connect 激活此回调。
     *
     */
    public class PushCallback implements MqttCallback {
    
        public void connectionLost(Throwable cause) {
    
            // 连接丢失后，一般在这里面进行重连
            System.out.println("连接断开，可以做重连");
        }
    
        public void deliveryComplete(IMqttDeliveryToken token) {
            System.out.println("deliveryComplete---------" + token.isComplete());
        }
    
        public void messageArrived(String topic, MqttMessage message) throws Exception {
            // subscribe后得到的消息会执行到这里面
            System.out.println("接收消息主题 : " + topic);
            System.out.println("接收消息Qos : " + message.getQos());
            System.out.println("接收消息内容 : " + new String(message.getPayload()));
        }
    }