The MQTT Interface allows FLOW devices to publish selected widget data and diagnostic information to external systems using the MQTT protocol. MQTT communication is based on a broker, which acts as a central server that receives and distributes messages between connected clients.

The interface is available by default for all FLOW devices under Interfaces->MQTT interfaces.

Figure: MQTT interface settings.

Configure the interface in FLOW according to the server (broker) setup, as follows:

Name – User-defined.
Address – MQTT broker address in the format:

mqtt://<host>:<port> - TCP
tcp://<host>:<port> - TCP
ws://<host>:<port> - Unsecure websockets
unix://<path>
SECURE:
wss://<host>:<port> - Secure websockets
mqtts://<host>:<port> - SSL/TLS
ssl://<host>:<port> - SSL/TLS

Quality of Service (QoS) – Delivery reliability.
- QoS 0 – At most once
- QoS 1 – At least once
- QoS 2 – Exactly once
Username / Password – Optional credentials used for broker authentication.
Use client certificate – Enables client certificate authentication.
Use CA certificate – Optional CA certificate for broker verification.
Verify server certificate – Verifies the broker TLS certificate against.
Disable hostname verification – Disables hostname verification against the certificate.
Topic prefix – User-defined topic prefix added to all published MQTT topics. Device ID is automatically added to the topic prefix.
Device ID type – Determines how the device identifier is generated in MQTT topics.
- Block name
- Custom
Show logs – Communication logs.

Outputs

The MQTT interface publishes selected outputs with a configured sending policy:

On create – Publish when a new event is created.
On update – Publish whenever the event is updated.
On closing – Publish when the event is closed.

Figure: Outputs list.

Figure: MQTT interface output definition.

Published Data

Depending on the selected outputs, MQTT can publish:

Widget snapshots (same payloads as Webhook outputs)
System and network information - part of system diagnostics
Network information
Processing state - block processing diagnostics, uptime, timestamp, memory usage etc.