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Chat Demo - HTML Client

The Chat Demo is a very simple chat application based on MQTT.Cool.

Live Demo

Live Demo

View live demo


The Chat Demo implements an extremely simple chat application, which shows a basic usage of the MQTT.Cool Web Client API to handle communications with MQTT.Cool. All the users connected to the page can exchange messages, therefore launch multiple instances of the demo, possibly on different machines, to appreciate the message broadcast capability.

Check out the sources for further explanations.

Overall Architecture

Here the overall architecture of the demo:


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
  • Launch the MQTT.Cool server.
  • Download this project.
  • As the latest version of the MQTT.Cool JavaScript library is always available through unpkg, it is hot-linked in the html page.


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

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

and change it accordingly.


Open your browser and point it to http://localhost:8080/ChatDemo, or to the address according to the host and/or the name of the folder where you deployed the project.

The demo is configured to establish an MQTT channel to the publicly accessible MQTT broker hosted at tcp://, but fill free to provide any broker address through the relative form fields; then, click Connect to start.

See Also

MQTT.Cool Compatibility Notes

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


The Chat Demo is a very simple chat application based on MQTT.Cool







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