This is a very basic demo of using the MQTT package with Node.js to send messages between a set of fake sensors, and a server.
This demo uses the free HiveMQ MQTT broker. You can read more about how MQTT works here.
Alternatively you could install your own MQTT broker, for example Mosquitto.
- Install Node.js
- Clone this repo, then:
cd nodemqtt
npm install
There are two components, the "server" (see server.js), and the "sensor" (see sensor.js). You should start one server and one or more sensor instances.
Start the server first, with:
npm start
If all goes well it should connect to the MQTT broker, and output something similar to:
$ npm start
> nodemqtt@0.0.1 start /Users/simon/source/projects/nodemqtt
> node server.js
Server is waiting for messages.
Nothing else will happen until you start at least one sensor.
Each sensor has an ID number. The one provided has ID 0 and is configured in package.json:
"scripts": {
"sensor": "node sensor.js 0"
},
To start this, simply use:
npm run sensor
Once started the sensor should push MQTT messages into the broker every 5 seconds, each message containing the sensor ID number and the current date and time. If running successfully, output from the sensor should look like:
$ npm run sensor
> nodemqtt@0.0.1 sensor /Users/simon/source/projects/nodemqtt
> node sensor.js 0
Started sensor 0
Sending data: 0|Thu Apr 20 2017 09:55:02 GMT-0700 (PDT)
Sending data: 0|Thu Apr 20 2017 09:55:07 GMT-0700 (PDT)
And if the server is running, it should start receiving messages and logging those:
$ npm start
> nodemqtt@0.0.1 start /Users/simon/source/projects/nodemqtt
> node server.js
Server is waiting for messages.
Registering sensor ID: 0
Received sensor message: 0|Thu Apr 20 2017 09:55:02 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:55:07 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:55:12 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:55:17 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:55:22 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:55:27 GMT-0700 (PDT)
To start more than one instance of the sensor, add more lines to the scripts section of package.json and invoke npm to run them e.g.:
"scripts": {
"sensor": "node sensor.js 0",
"sensor1": "node sensor.js 1"
},
Then start sensor1:
npm run sensor1
The server should then start reporting output from both sensors:
Received sensor message: 0|Thu Apr 20 2017 09:58:22 GMT-0700 (PDT)
Registering sensor ID: 1
Received sensor message: 0|Thu Apr 20 2017 09:58:27 GMT-0700 (PDT)
Received sensor message: 1|Thu Apr 20 2017 09:58:29 GMT-0700 (PDT)
Received sensor message: 0|Thu Apr 20 2017 09:58:32 GMT-0700 (PDT)
Received sensor message: 1|Thu Apr 20 2017 09:58:34 GMT-0700 (PDT)
Basic configuration information is contained in common.js which exposes an object containing topic names and broker URL:
module.exports = {
MQTT_BROKER: 'broker.hivemq.com',
REGISTER_TOPIC: 'sensor/register',
DATA_TOPIC: 'sensor/data'
};