MQTT Reception - “Parameters” -> “Publish”

Publish: Configuration of the publish parameters.

• Publish Parameters: In this section, the publication Topic and the Quality of Service of the message can be defined. Furthermore, the Retained Message option can be selected.

The QoS of the message specifies the quality of service used to send the message to the Broker.

When the Retained Message option is selected, the channel considers each message as Retained. Since there can only be one Retained message, each time a new message is sent through this channel, it overwrites the previous one; meaning each Retained message will remain in memory until other message replace it.

• Payload Parameters: Configuration of parameters to modify the payload while it is processed. If the protocol is XML, there are three different options:

  • Entired Message: The full message is processed. It is the only available option for JSON.

• • XPath Expression (Text Value): Only the defined value is collected from the source XML, parsing it as a text string. If the protocol is XML, the encoding of the text to be processed must be defined.

• • XPath Expression (Node Element): The defined element and all its sub-elements are collected from the source XML. These elements will be processed as a new XML. If the protocol is XML, the encoding of the new XML file to be processed must be defined.

The CheckBox “Base64 decode received PI message” allows to decode the Base 64 message received from PI, and the CheckBox “Base64 encode broker message” encodes to Base64 the payload before it is published in the Broker.