Generally people choose MQTT because it is lightweight and very well tested. I personally use it because its light one source, scalable, and very flexible. Hav

Generally people choose MQTT because it is lightweight and very well tested. I personally use it because its light one source, scalable, and very flexible. Have also chosen to use CoAP rather than REST for ad hoc data requests because for constrained devices it is much lighter on bandwidth, simpler to use than typical REST over TCP+HTTP with which most people are familiar. In IOT its hard to go past MQTT for the usual signals paired with CoAP for ad hoc. When I want to reduce dependencies or just being lazy even CoAP gets replaced with building a request/respond mechanism using a MQTT queue so a hub pubs a message to the devices command queue and device reads that queue and responds to it. How often device checks the command queue depends on whether or not device can run command queue monitoring asynchronously or must do a scheduled round-robin of the queues. The Eclipse Paho libs have been great for me using across different OS and bare metal, Arduino, FreeRTOS.