A MQTT command receiver for Apache Flink, using MQTT.fx to perform test

1. Download mqtt.fx 1.7.1

2. Install mosquitto server on your virtual machine or server by linux command:

   $ sudo apt install -y mosquitto
   

3. Use this command to check the status of mosquitto server, where it should be both active and loaded

   $ sudo systemctl status mosquitto
   

4. After installation, mosquitto should be automatically started. If not use this command to manually start it:

   $ sudo systemctl start mosquitto
   

   Moreover, use this command to stop it:

   $ sudo systemctl stop mosquitto
   

   Or restart it:

   $ sudo systemctl restart mosquitto
   

5. Install Mosquitto Clients using this command:

   $ sudo apt install -y mosquitto-clients
   

6. A TOPIC is like a relative path but in IoT setting, like: home/living_room/TV, home/bathroom/toilet, home/garden/fountain, etc. You can subscribe a topic by command line:

   $ mosquitto_sub -t [TOPIC NAME]
   

   For example:

   $ mosquitto_sub -t "home/living_room/TV"
   

7. You can push notifications using command, for example, set the TV in the living room ON:

   $ mosquitto_pub -m "ON" -t "home/living_room/TV"
   

   Since we use mqtt.fx, it is not necessary to use command to subscribe and push commands.

8. Open mqtt.fx, click the gear icon, connect to localhost: 1883, we choose 1883 because it does not need any authentication to connect. Then specify the username, password, hostname,clientID and msgTopic properties for object MqttConfig in line 24 in MqttConsumer.java

   The values of username, password, hostname and msgTopic should be the SAME as those in mqtt.fx configuration, while clientID should be DIFFERENT with the one in mqtt.fx! Or you will get frequently kicked out whenever you try to connect to both clients.

9. Start both mqtt.fx client and the java program, pushing notifications on mqtt.fx and you should be able to see the commands on the terminal where you run Java program.