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MQTT Publisher
The MQTT publisher provides a northbound data interface for MQTT clients to data point values within the WinCC OA project.
Configuration of the MQTT Publisher
Advanced
Advanced tab that allows to define advanced settings, like Root Topic, Intervals and Client ID.

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- MQTT Publisher
  The MQTT publisher provides a northbound data interface for MQTT clients to data point values within the WinCC OA project.
  - Requirements and Installation
  - Configuration of the MQTT Publisher
    - Connection
      General connection parameters like host and port number. Depending on the configuration a redundant connection can also be configured.
    - Advanced
      Advanced tab that allows to define advanced settings, like Root Topic, Intervals and Client ID.
    - Certificate
      Certificate tab that allows to define a client-side certificate that is be used for the communication with the MQTT broker.
    - Default / Last Will
      Common settings for the MQTT messages as well as Last Will settings.
    - State Details
      Details about the current state of the connection as well as general message statistics.
    - Commands
    - State
  - Data Access for the MQTT Publisher
  - Internal data points of the MQTT Publisher
  - Notes and Restrictions
  - [mqttpub]
    Settings for the MQTT Publisher.
  - How-To
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Advanced

Advanced tab that allows to define advanced settings, like Root Topic, Intervals and Client ID.

Figure 1. Advanced settings tab

Advanced configuration

Root Topic: The root topic that should be used for publishing to the MQTT broker.
Enable statistics: Enables the statistical evaluation of data for this connection.
Persistent session: If the setting "Persistent Session" is enabled, the internal Client ID is composed of connection name and data point ID of the connection data point. If the setting is not enabled the internal client ID is generated uniquely or can be manually stated, see below. For more information on the Persistent session, see Persistent Session.
Max. Topic Alias: Topic alias can be used to reduce network traffic, because the publisher uses an alias (number) instead of the usually much longer topic string for publish. This setting allows to define the maximum number of allowed topic aliases. By default no topic aliases are used.

Note:
When using topic aliases with MQTT Version 5 the used broker must support 65535 maximum topic aliases, otherwise the connection will be unstable. If the broker does not support the usage of 65535 topic aliases it is recommended to disable topic aliases in general.

Intervals / timeouts

Keep alive interval: The driver recognizes a loss of connection after the defined keep alive timeout.

Client ID

Identifier: Optional Client ID that can be entered if it is required by the MQTT broker.

Auto IGQ

Settings for an automatic inverse general query.

Publish on connect: When connecting an inverse general query will be performed and published.
Publish on redu switch: When a redundancy switch is performed, an inverse general query will be performed and published.