Now, we will take advantage of the last will and testament feature. We will create the main class named Main that uses the asynchronous API of the Paho Java Client, the previously coded SecurityHelper class to establish an encrypted connection with an MQTT server, and the SensorsManager class to process the received messages with commands. The code will configure a message to be sent as the last will when the connection is lost. In addition, the Main class will call the loop method for a SensorsManager instance to publish messages with data retrieved from the sensors when they are turned on with the appropriate commands.
We will split the code for the Main class into many code snippets to make it easier to understand each code section. The following lines declare all the necessary imports. The code file for the sample is included in the mqtt_essentials_gaston_hillar_04 folder, in the Java02/src/Main.java file:
package com.packt.mqttessentials.Sensors02...
