MQTT in Sensor-Online — Subscribe and Publish
Sensor-Online supports MQTT in both directions: as a subscriber (consuming data from external brokers) and as a publisher (pushing sensor data to your own broker or third-party systems). Full Sparkplug B encoding is included, enabling seamless integration with industrial SCADA systems and historian databases that rely on structured payloads.
What Is MQTT and Why Does It Matter?
MQTT (Message Queuing Telemetry Transport) is a lightweight publish-subscribe protocol designed for constrained devices and low-bandwidth networks. A sensor publishes a measurement to a topic; every system subscribed to that topic receives it immediately. The protocol is used in everything from home automation to large-scale industrial control systems.
Key advantages of MQTT in IoT deployments:
- Very low protocol overhead — ideal for battery-powered sensors and NB-IoT devices
- Asynchronous delivery — publishers and subscribers operate independently
- QoS levels (0, 1, 2) — control delivery guarantees per message
- Last Will and Testament — automatically notify subscribers if a device disconnects unexpectedly
Sparkplug B Support
Sparkplug B is a specification built on top of MQTT that standardises topic namespacing, payload encoding (using Google Protocol Buffers) and device state management. It is the most widely adopted standard for connecting IoT data to industrial applications such as Ignition by Inductive Automation, Kepware and similar SCADA/historian platforms.
Sensor-Online publishes sensor data as Sparkplug B NBIRTH, NDATA and NDEATH messages, making it straightforward to subscribe from any Sparkplug-compatible application without custom parsing.
Typical MQTT Integration Scenarios
- Push to external SCADA — Publish LoRaWAN sensor values from Sensor-Online to a plant historian or SCADA via MQTT broker
- Receive from external devices — Subscribe to a broker where M-Bus or Modbus gateways publish their readings, centralising all data in Sensor-Online
- BMS integration — Feed room temperature, CO₂ and humidity to a building management system via MQTT without API polling
- Cloud-to-cloud — Bridge data between Sensor-Online and cloud platforms like AWS IoT Core or Azure IoT Hub using standard MQTT
Configuring MQTT in Sensor-Online
MQTT connections are configured directly in the Sensor-Online administration panel. You specify the broker address, port, authentication credentials and the topic structure. For Sparkplug B, you select the Sparkplug B output format and map your device groups to the appropriate namespace. No coding is required.
For Node-RED users, the combination of Sensor-Online’s MQTT output and Node-RED’s MQTT nodes provides a no-code way to build custom routing, transformation and forwarding workflows between systems.
FAQ: MQTT and Sparkplug B in Sensor-Online
Which MQTT brokers are supported?
Sensor-Online connects to any standard MQTT broker — Mosquitto, HiveMQ, EMQX, AWS IoT Core, Azure IoT Hub and others. TLS/SSL connections and username/password authentication are supported.
Can Sensor-Online act as both subscriber and publisher simultaneously?
Yes. A single Sensor-Online instance can subscribe to incoming data from one broker while publishing to a different broker or topic namespace at the same time.
Is Sparkplug B required for SCADA integration?
No, but it is strongly recommended if the target SCADA or historian natively supports Sparkplug B. It removes the need to write custom payload parsers and ensures device state (birth/death certificates) is tracked correctly.
Learn more about Sensor-Online’s integration capabilities or explore the knowledge base for configuration guides.
