Eclipse Foundation, the independent organization supporting the Eclipse project open source, recently made a survey about the most popular messaging protocols used in IIoT applications, obviously referring to wireless communications. Thanks to its features of simplicity, efficiency, and lightness, MQTT (Messaging queuing telemetry transport) is the most popular choice. It is adopted by all the main Scada and the most advanced industrial connectivity systems.
A great choice to be used in combination with Arm-based architectures is MQTT Client of Segger, we support and distribute in Italy.
If you want to know more, link here: http://www.tecnologix.it/mqtt-client-per-realizzare-applicazioni-iot-e-m2m