Fig. 2.

Typical wireless connection between one controller (client), an MQTT broker (server) and a computer (sender). All devices must be connected to the same network in order to operate. The injector (A), the server (C) and client (D) are thus connected on the same router (B). The blue arrows represent the WIFI connections. An Orange pi Zero is used as an MQTT broker and also creates a graphical user interface (D). When a command is entered on the graphical interface, it is sent to the router, relayed to the MQTT broker before being sent to the injector via the router. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)