MTConnect
A standard vocabulary and structure for machine data, served over HTTP by an agent. Read-only by design. Strong where you want comparable machine-tool data from many vendors with little effort.
OPC UA
A platform-independent industrial communication standard (IEC 62541) with an information model, client/server and publish/subscribe communication, and built-in security including certificates, signing and encryption. It can read and also write, so access control matters. Industry-specific companion specifications define models for particular equipment types.
MQTT
A lightweight publish/subscribe messaging protocol standardised by OASIS and ISO. It moves messages between publishers and subscribers via a broker and says nothing about what the payload means. Specifications such as Sparkplug add a topic structure and payload definition for industrial use. MQTT is also a transport for OPC UA publish/subscribe.
How they combine
A typical factory has all three. A machine might expose OPC UA, a gateway might publish MTConnect-derived data over MQTT, and a sensor might speak MQTT directly. The meaningful work is mapping each to a common model and keeping the origin of each value.
A practical rule
Read-only monitoring is the simplest first step and the safest. Treat any path that can write to a machine as a safety-relevant interface with explicit limits, approval and verification.
Standards and further reading
- IEC 62541 — OPC Unified Architecture
- OASIS MQTT / ISO/IEC 20922
- Eclipse Sparkplug specification
- MTConnect Institute documentation