MQTT vs Modbus vs BACnet: What These Protocols Actually Do

MQTT is a lightweight publish-subscribe messaging protocol built for IoT devices with limited bandwidth or power — a sensor 'publishes' a reading, and anything subscribed (a dashboard, an automation rule) receives it. It's become close to a default standard for modern smart-home and IoT device communication because it's efficient and widely supported.

Modbus is an older, simpler protocol widely used in industrial equipment, PLCs and building systems — it's not glamorous, but it's the protocol behind a huge share of existing meters, drives and controllers, which is exactly why integration projects need to speak it fluently rather than assume everything is modern.

BACnet is specifically designed for building automation — HVAC, lighting, access control — and is the standard most Building Management Systems are built around. Unlike MQTT or Modbus, it was designed from the start with building-specific concepts (zones, schedules, alarms) baked in, which is why a BMS project typically centres on it.

In practice, the protocol a project needs to support is decided by the equipment already installed, not preference — a factory full of Modbus-speaking PLCs needs Modbus integration regardless of what's more modern. The real skill in a project like this is bridging protocols the existing equipment actually uses into a modern dashboard, not replacing hardware to standardise on one protocol.