Documentation of the Elvis package “MQTT”
Overview
MQTT is a communication protocol from the IoT sector. See also https://de.wikipedia.org/wiki/MQTT and http://mqtt.org/.
Procedure
After inserting the package into the server project via the package manager (from Elvis 3.3.114), the new connection driver “MQTTDriver” is available.
The next step is to create a new data point connection in the server project: Right-click on the server project – add -> add server data ->> connection with data points. The corresponding *.elvissc file should be given a corresponding name.
Then create a first table entry, i.e. a new port instance, in this file by clicking on the green cross, and select the option “MQTTDriver” in the “Driver type” column. The configuration of this new port is done in the properties window; at least the host name of the MQTT broker must be specified.
Now you can create data points for this connection for the individual data to be transmitted. The MQTT topic name is specified as the address.
Details
Persistent Session
The port uses a persistent session when there are receiving data points. If something is changed at the assigned data points in the designer, a new session ID is created, so that a persistent session that may have already been shown in an earlier run is discarded.
Quality Of Service (QOS)
By default, “At least once” (1) is used for value data points, and “Exactly once” (2) is used for command data points. A different QOS level can be specified as “Q=0”, “Q=1” or “Q=2” in the server info of the data point type.
Retain
The retain flag is set for value data points, but not set for command data points.
Release notes with release notes (PDF)
