MQTT vs OPC UA: What Is the Difference in Industrial Systems?
Message transport, industrial information models and where each protocol fits.
MQTT and OPC UA are both used in industrial environments, but they solve different problems.
MQTT transports messages. OPC UA exchanges industrial data with structure and meaning. Understanding the difference helps when connecting PLCs, SCADA, IIoT and cloud services.
MQTT: lightweight messaging
MQTT uses publish/subscribe communication. Devices publish messages to a broker, which distributes them to subscribed clients.
A typical flow is PLC → MQTT Broker → SCADA / Cloud / Analytics.
It is commonly used for telemetry, remote monitoring and cloud integration, with low protocol overhead. Common ports are TCP 1883 and TLS 8883.
MQTT does not define what an industrial value means. A temperature reading of 85 still needs an agreed format to identify the unit and equipment. Sparkplug B helps standardize industrial MQTT data.
OPC UA: structured industrial information
An OPC UA server exposes objects, variables, methods, events and references. Clients can browse that structure to discover data and understand relationships between equipment.
A typical flow is SCADA / HMI → OPC UA Server → PLC / Industrial Devices.
OPC UA supports both Client/Server and PubSub communication. TCP 4840 is the common port for OPC UA TCP.
Choose by the task
- MQTT: distribute messages to multiple systems, especially for telemetry and cloud integration.
- OPC UA: discover, access and exchange structured industrial information.
Both support secure communication. MQTT deployments commonly use TLS, authentication and broker access controls. OPC UA supports certificates, authentication, signing and encryption. Security depends on implementation and configuration.
The protocols can also work together: OPC UA PubSub can use MQTT as its transport.
Explore both in Labshock
Logfall introduces MQTT communication in an industrial environment. Mindrock focuses on OPC UA and its information model.
Explore their communication from an OT security perspective, connect messages to the process and understand what the data represents.
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