Automation and IIoT
What is MQTT?
MQTT is a lightweight publish subscribe messaging protocol for IoT. Brokers, topics, QoS levels, Sparkplug, and how MQTT is used in manufacturing data hubs.
Quick answer
MQTT is a lightweight publish subscribe messaging protocol designed for devices on limited or unreliable networks. Clients publish messages to topics on a central broker, and any client subscribed to a topic receives them. It is an OASIS standard and is widely used to move industrial data from edge gateways to MES, dashboards and cloud platforms.
Updated 30 October 2026. Written by the Ajinkya Technologies engineering team, reviewed by Amey Kadle.
MQTT explained
MQTT decouples senders from receivers. A machine gateway does not need to know who uses its data; it publishes to a topic such as plant/line1/press/count, and the MES, a dashboard and a historian each subscribe. Adding a new consumer does not touch the producer, which is the main reason MQTT underpins the unified namespace approach to plant data.
The protocol is small and efficient. It offers three quality of service levels (at most once, at least once, exactly once), retained messages so a new subscriber gets the last known value immediately, and a last will message that tells others when a client disconnects unexpectedly. Version 3.1.1 and version 5.0 are both OASIS standards; 5.0 adds features such as message expiry and user properties.
MQTT defines how messages move, not what they contain. Industrial users therefore agree payload and topic conventions, for example with the Eclipse Sparkplug specification, which defines state management and payload structure for industrial devices. Security comes from TLS encryption, authentication and topic level access control on the broker.
Key concepts
- Publish subscribe through a broker
- Topics decouple producers from consumers
- QoS 0, 1 and 2; retained messages; last will
- OASIS standard, versions 3.1.1 and 5.0
- Sparkplug adds industrial payload conventions
Questions
What is an MQTT broker?
The server that receives all published messages and delivers them to subscribers of each topic. Common brokers include Mosquitto, HiveMQ and EMQX.
Is MQTT better than OPC UA?
They solve different problems. MQTT is a light transport for distributing data; OPC UA adds rich information models and is common at the machine. Many architectures use both.
What happens to MQTT data if the network drops?
With store and forward on the edge gateway and QoS 1 or 2, messages are buffered locally and delivered in order when the connection returns, so no counts are lost.
References
How we help with MQTT
We build MQTT based data hubs where edge gateways publish machine data once and MES, dashboards and SAP integrations subscribe, with buffering so outages lose nothing.
Interactive 3D demo with simulated data: cut the network and watch the edge store and replay.
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