Awesome

hu.dwim.mosquitto

A Common Lisp FFI for Mosquitto (an MQTT implementation)

Status

I've played with it for a while at around 2016, but that was it for me. Anyone willing to take over its maintenance is welcome to it!

Its FFI part is auto-generated using c2ffi, so it should be pretty comprehensive. What may be missing is some convenience utils on the Lisp side.