Sending Data Through MQTT

Setting Up The Function Node

This is an optional step. The Function Node is used to transform the ’msg’ object sent by the Client node. The MQTT node sends out the ’msg.payload’ field of the ’msg’ object. This means that it only sends the value it just read but doesn’t indicate which Item node this value is connected to. To address this, we will take the ’msg’ object and create a new one, where ’msg.payload’ contains four fields: timeStamp, topic (which corresponds to the item field in the Item Nodes), browseName and payload as seen in #fig:function-node[2.6].

Function Node

Setting Up The MQTT Out Node

First, we need to set up the Server field. To do this, click the pen icon located to the right of the field#fig:mqtt-merge[2.7]. This action opens a tab for configuring the broker.

Setting up the broker:

  • Server field: Here, we enter the IP and PORT of the MQTT broker.

  • Other fields can be left at their default values.

Afterward, we configure the Topic field, to the topic which we wish to publish on. Other fields can be left at their default settings.

image::step2-mqtt.png[Left side: Properties of the MQTT Broker. Right side: Properties of the MQTT Out node]

Now we connect the Client node to the Function node and the Function node to the MQTT out node#fig:client-func-mqtt[2.8].

Client to Function to MQTT node connection