In the previous chapters, you learned how MQTT works in detail. We understood how to establish a connection between an MQTT client and an MQTT server. You learned what happens when you subscribe to topic filters and when a publisher sends messages to specific topics. In this chapter, we will use MQTT over TCP again, and we won't use MQTT over WebSockets.
Now, we will use Swift, specifically Swift 3, as our main programming language to generate MQTT clients that will act as publishers and subscribers. We will connect an iOS app as an MQTT client to the MQTT server, and we will process simple commands to control actuators with MQTT messages and display status messages received from the boards that control the actuators.
In this case, we want to create a simple iOS app that we will use at home, and therefore, we won't be working with TLS at all. Then, we will code a Node.js script that will run on the boards that have actuators wired to them. In the previous chapter...