Sending and receiving data in real-time through Internet with PubNub

In Chapter 4, Working with a RESTful API and Pulse Width Modulation, we developed and consumed a RETful API that allows us to control electronic components connected to our Intel Galileo Gen 2 board through HTTP requests. Now, we want to send and receive data in real-time through the Internet and a RESTful API is not the most appropriate option to do this. Instead, we will work with a publish/subscribe model based on a protocol that is lighter than the HTTP protocol. Specifically, we will use a service based on the MQTT (short for MQ Telemetry Transport) protocol.

The MQTT protocol is a machine-to-machine (short for M2M) and Internet of Things connectivity protocol. MQTT is a lightweight messaging protocol that runs on top of the TCP/IP protocol and works with a publish-subscribe mechanism. It is possible for any device to subscribe to a specific channel (also known as topic) and it will receive all the messages published...