MQTT, Subscriber

see also protocol(s)

  • 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:

    • MQTT V3.1
    • MQTT V3.1.1

    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
Publish/Subscribe Pattern
  • Simple Overview MQTT Subscriber, MQTT Publisher
This protocol stack can be used with following products
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  • ipELB
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