mqtt

<dependency>
    <groupId>org.eclipse.paho</groupId>
    <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
    <version>1.2.5</version>
</dependency>

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

public class MQTTReceiver {
    
    public static void main(String[] args) {
        String brokerUrl = "tcp://localhost:1883"; // Change this to the URL of your MQTT broker
        String clientId = "mqtt_receiver";
        MemoryPersistence persistence = new MemoryPersistence();
        
        try {
            MqttClient client = new MqttClient(brokerUrl, clientId, persistence);
            
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setCleanSession(true);
            
            System.out.println("Connecting to broker: " + brokerUrl);
            client.connect(connOpts);
            System.out.println("Connected");
            
            client.subscribe("myTopic", new MqttMessageListener());
            
        } catch (MqttException e) {
            System.out.println("Exception caught: " + e);
            e.printStackTrace();
        }
    }
    
    private static class MqttMessageListener implements IMqttMessageListener {
        public void messageArrived(String topic, MqttMessage message) throws Exception {
            System.out.println("Received message on topic " + topic + ": " + message.toString());
        }
    }
}