Hello IoT World Demo - Node.js Client

The Hello IoT World Demo is a simple real-time telemetry application based on MQTT.Cool.

Details

The Hello IoT World Demo uses the MQTT.Cool Node.js Client API to show how MQTT.Cool can be used to send real-time telemetry data through the Web.

In this demo, a Node.js client application submits two MQTT subscriptions to two separate topics, in order to receive real-time telemetry metrics from a hypothetical car, such as Speed and Engine RPM. Upon receiving, data message is displayed on the console.

Real-time telemetry updates are delivered by a random feed simulator, which is a pure MQTT Node.js client that connects to an MQTT broker, generates simulated data and publishes them to the target topics at a fixed interval (100 ms).

The demo shows how MQTT.Cool enables an end-to-end connection between the Node.js client application and the MQTT broker, as it takes the role of real MQTT server proxy by acting as an intermediary for requests coming from the client and targeted to the broker (in this case, the subscriptions to telemetry topics), as well as for responses (subscription acks) and Application Messages (telemetry data) coming from the broker and directed to the client.

Overall Architecture

Here the overall architecture of the demo:

Install

If you want to install a version of this demo pointing to your local MQTT.Cool, follows these steps.

• As prerequisite, this demo needs an up and running MQTT broker. You can choose whatever MQTT broker you prefer, or may also use one of the available public broker (an up-to-date list is maintained at https://github.com/mqtt/mqtt.github.io/wiki/public_brokers).

• Configure an MQTT.Cool instance. Please refer to mqtt.cool web site download page to find the MQTT.Cool download package. MQTT.Cool comes with a set of predefined configurations for connecting with local MQTT server instances, as well as with the most common publicly accessible brokers. If you want to provide a new custom configuration, open the brokers_configuration.xml file located under <MQTT.COOL_HOME>/conf and provide a set of entries similar to the following (please refer to the inline documentation for more in-depth information on how to configure broker connection parameters):

  ...
  <!-- MQTT broker connection parameters for a local instance
       listening on port 1883, aliased by "mybroker". -->
  <param name="mybroker.server_address">tcp://localhost:1883</param>
  <param name="mybroker.connection_timeout">5</param>
  <param name="mybroker.keep_alive">20</param>
  ...

• Launch the MQTT.Cool server.

• Download this project.

• If required, install Node.js

• From the src/client folder, locally install the client application (based on the MQTT.Cool Node.js Client API), by using npm:

  $ npm install

• From the src/feed folder, locally install the feed simulator application:

  $ npm install

Configure

The demo assumes that the MQTT.Cool server is launched from localhost, but if you need to target a different server, search in src/client/client.js this line:

const MQTT_COOL_URL = 'http://localhost:8080';

and change it accordingly.

Further, the demo will look for the mosquitto alias, which is one of the predefined configurations in brokers_configuration.xml. Once more, if you need to target a different MQTT broker, and provided that relative connection parameters are already defined as shown above, modify the following line in src/client/client.js:

var mqttClient = mqttCoolSession.createClient('mosquitto');

and change it by replacing mosquitto with the new alias that maps the MQTT broker you are going to use.

Launch

From the src/feed folder, run the feed simulator application to publish simulated telemetry data:

$ node feed.js <url_broker>

where url_broker is the url of the MQTT broker relative to the alias in use in the client application.

From the src/client folder, run the client application:

$ node client.js

and immediately the console reflects updates according to the received real-time metrics.

See Also

• Check out all other demos on MQTT.Cool site

MQTT.Cool Compatibility Notes

• Compatible with MQTT.Cool SDK for Node.js Clients version 1.0.0 or newer.
• Compatible with MQTT.Cool since version 2.0.0 or newer.