Use your web browser to connect to an MQTT broker and create alerts based on the messages that you receive. It is also possible to connect to a serial device and send commands (e.g., make an LED blink) based on the alerts that you created. Another feature is the ability to receive messages from a serial device and publish these messages to a specific topic with the help of a JavaScript decoder.


m-serial mqtt serial port

This m-serial app brings MQTT and serial devices to your web browser! Now you can connect to an MQTT broker and create alerts based on the messages that you receive. You can also publish messages generated by your serial device. By running everything in the browser, you don’t need to install anything, and you are also safe because everything runs on the client side (nothing is sent to an external server).

Visit at m-serial


  • MQTT

Exclusive support for MQTT over WebSockets. MQTT over WSS enables seamless data flow through any web browser, significantly advancing the accessibility of the IoT world. To configure the host file make sure to have something similar to this:

  • Alerts

Create alerts rules based on the words received from the subscribed MQTT topic. These rules can create actions like Browser alerts or send commands to serial device connected.

  • USB

Enabling the Serial option allows alert rules to send commands to the connected serial device. When the Decoder is enabled, it becomes possible to publish the device’s output (and modify it) to a specific topic configured in the JavaScript function.

function (message) {
  var tmp = {};
  var topic = "/m-serial-test";   //Your Topic

  tmp.topic = topic;
  tmp.message = message;

  return tmp;

One thing that you need to consider is that the USB serial port biggest problem is compatibility with the web browsers. At the time of writing this, only Chrome, Edge, and Opera support the Web Serial API needed to make this work. Phone or Tablet users are also out of luck for now

m-serial mqtt serial port