Formal Specification and Verification of MQTT Protocol in PlusCal-2

The recent rise in adaptation of Internet of Things (IoT) concepts has potential to transform industries such as healthcare, manufacturing and power-grids. The communication protocols are at the heart of IoT and one such lightweight protocol being in widespread use is the Message Queue Telemetry Transport (MQTT) protocol. In this paper, we address the need to verify the correctness of the MQTT protocol. We have proposed a PlusCal-2 and TLA+ based formal model to both model check the safety and liveness properties and provide execution traces in case of any violation. We have detailed our models and provided performance analysis results to explain the practicality of our technique.