MQTT, Subscriber connects to an MQTT broker, subscribes to the configured topics and processes the published MQTT messages.
The received MQTT publish payload is decoded according to a user defined template and applied to the associated data point. There is no publishing of data points towards the MQTT broker.
Supported versions:
Transport Layer:
- TCP/IP with or without TLS (configurable)
Security mechanisms:
- Authentication with user and password
- Usage of X.509 certificates
- TLS with PSK
Data processing:
- Supported QoS 0,1,2
- Flexible payload decoding due to templates
- Identifiying data points
- + by topic
- + by explicit address field in payload
- Decoding multiple data points in payload
- Monitoring of data point updates
- Support for wildcards in topic
Operating mode
At startup, a list of topics is created over all data points and subscribed to an MQTT broker. After receiving a published MQTT packet, the appropriate template for decoding the payload is determined and the extracted data point attributes are applied to the process information. If a connection interruption occurs, the process image is set invalid.
Optionally, a monitoring per data point can be configured which will check if the process value was updated within the configured time interval, to detect a disconnected/broken MQTT publisher. If the process value was not updated, it is set invalid.
Following data point attributes can be applied:
- Address
- Timestamp
- Value
- Quality
