MQTT Simulator

The Edge Xpert MQTT Device Service provides an MQTT simulator. This is implemented with mqtt-scripts, a Node.js-based script runner for use in MQTT smart homes.

This is shipped with Edge Xpert and can be found in /usr/share/edgexpert/examples/device-services/mqtt/simulator/mqtt-scripts as the file room.js.

Simulated Values

The MQTT script simulates a room sensor. It generates random values for the humidity and temperature of a room, whether a switch is turned ON or OFF, and the room number.

The device simulator supports the following behaviors:

Publish room sensor data every 30 seconds
Receive a request for readings and return the room number
Receive a put request and change the room number accordingly

The following resources and commands are defined in the provided device profile (usr/share/edgexpert/examples/device-services/mqtt/simulator/simulator.profile.yml) and are detailed below:

Resource	Read/Write
`switch`	Read only
`temperature`	Read only
`humidity`	Read only
`number`	Read and Write

Command	Included Resources
room	Reads `switch`,`temperature`, and `humidity` values
roomNumber	Reads and writes to `number`

Run the Simulator

Query the MQTT broker IP for the simulator's MQTT connection:

$ edgexpert ip | grep mqtt-broker
Name                          |IP
---------------------------------------------
mqtt-broker                   |172.20.0.3

The MQTT room simulator can be run with the following command:

docker run -d --restart=always --name=mqtt-scripts --network=host \
    -v /usr/share/edgexpert/examples/device-services/mqtt/simulator/mqtt-scripts:/scripts \
    dersimn/mqtt-scripts --url mqtt://172.20.0.3 --dir /scripts

Note

Replace mqtt://172.20.0.3 with the MQTT broker IP for your own Edge Xpert deployment. This can be retrieved through using the command edgexpert ip

After deploying Edge Xpert, we can inspect the broker connection of the simulator:

$ docker logs mqtt-scripts
2022-06-24 07:54:25.220 <info>  mqtt-scripts 1.2.2 starting
2022-06-24 07:54:25.319 <info>  mqtt connected mqtt://127.0.0.1
2022-06-24 07:54:25.830 <info>  /scripts/room.js loading

If you want to make changes to the script, create a local copy of this script in your working directory and make changes to this copy. Replace the file path in the command with your own.

Connecting to the Simulator with Edge Xpert

Once both the Edge Xpert MQTT Device Service and the simulator are running, you can connect to the simulator by simply adding a device to the device service.

When asked for a device name, 'MQ_DEVICE' should be used. This is the device name specified in the room.js script, which must match the name of the Edge Xpert device. If this has been changed in a local copy, use the new name instead.