PubExample.java

package MQTT;

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

public class PubExample {
    public static void main(String[] args) {
        MqttClient client;
        String broker = "tcp://localhost:1883";
        String clientId = MqttClient.generateClientId();
        String topic = "home/sensors/light";
        int qos = 2;

        //brew services start mosquitto

        try {
            client = new MqttClient(broker, clientId);
            MqttConnectOptions connOpts = new MqttConnectOptions();
            connOpts.setCleanSession(true);
            //connOpts.setUserName(username); // optional
            //connOpts.setPassword(password.toCharArray()); // optional
            //connOpts.setWill("this/is/a/topic","will message".getBytes(),1,false);  // optional
            //connOpts.setKeepAliveInterval(60);  // optional

            // Connect the client
            System.out.println(clientId + " Connecting Broker " + broker);
            client.connect(connOpts);
            System.out.println(clientId + " Connected");

            String payload = String.valueOf(0 + (Math.random() * 10)); // create a random number between 0 and 10
            MqttMessage message = new MqttMessage(payload.getBytes());

            // Set the QoS on the Message
            message.setQos(qos);
            System.out.println(clientId + " Publishing message: " + payload + " ...");
            client.publish(topic, message);
            System.out.println(clientId + " Message published");

            if (client.isConnected())
                client.disconnect();
            System.out.println("Publisher " + clientId + " disconnected");



        } catch (MqttException me ) {
            System.out.println("reason " + me.getReasonCode());
            System.out.println("msg " + me.getMessage());
            System.out.println("loc " + me.getLocalizedMessage());
            System.out.println("cause " + me.getCause());
            System.out.println("excep " + me);
            me.printStackTrace();
        }
    }
}