barnowl-mqtt

barnowl-mqtt collects ambient IoT data from a MQTT broker, transforming it into standard developer-friendly JSON that is vendor/technology/application-agnostic.

barnowl-mqtt is a lightweight Node.js package that can run on resource-constrained edge devices as well as on powerful cloud servers and anything in between. It is included in reelyActive's Pareto Anywhere open source middleware suite, and can just as easily be run standalone behind a barnowl instance, as detailed in the code examples below.

Quick Start

Clone this repository, install package dependencies with npm install, and then from the root folder, at any time, run either:

npm start

for barnowl-mqtt to attempt to connect to a local MQTT broker (mqtt://localhost).

npm start 12.34.56.78 8883

for barnowl-mqtt to attempt to connect to a MQTT broker at the given IP address and port.

In either case, barnowl-mqtt will subscribe to the pareto/v1/# topic, and (flattened) raddec JSON will be printed to the console.

Hello barnowl-mqtt!

Developing an application directly from barnowl-mqtt? Start by pasting the code below into a file called server.js:

import Barnowl from "barnowl";
import BarnowlMqtt, { MqttListener } from "barnowl-mqtt";

const barnowl = new Barnowl({ enableMixing: true });

barnowl.addListener(BarnowlMqtt, {}, MqttListener, {}); // See options below

barnowl.on("raddec", (raddec) => {
  console.log(raddec);
  // Trigger your application logic here
});

Supported Listener Interfaces

The following listener interfaces are supported by barnowl-mqtt.

MQTT

Connect to a MQTT server and subscribe to one or more topics to receive messages:

let options = { url: "mqtt://localhost", topics: [ "v1/reelyactive/local/#" ],
                clientOptions: { username: "user", password: "pass" } };
barnowl.addListener(BarnowlMqtt, {}, MqttListener, options);

The clientOptions are defined in the MQTT.js Client constructor documentation.

MQTT Topic Hierarchy

The following topic hierarchy is observed by barnowl-mqtt:

pareto/<version>/<tenant>/<location>/<device_type>/<device_id>/<device_id_type>/<function>

The path elements are as follows:

| Element | Default | Description | |:---------------|:------------|:------------------------------------------| | pareto | pareto | Hierarchy/protocol for Pareto Anywhere | | version | v1 | Topic hierarchy version | | tenant | reelyactive | Organisation (for multi-tenancy) | | location | local | Site or logical grouping (for multi-site) | | device_type | device | Optional device classification | | device_id | n/a | Unique device (radio-)identifier | | device_id_type | n/a | See Cheatsheet #idtype | | function | tlm/raddec | Topic function (ex: radio decoding telemetry) |

For example, by default, barnowl-mqtt would interpret the following as a radio decoding (raddec) from a Bluetooth Low Energy device with random (i.e. type 3) identifier ba:da:55:be:ac:04 on a local (i.e. non-remote) deployment of the reelyActive organisation:

pareto/v1/reelyactive/local/device/bada55beac04/3/tlm/raddec

Note that all elements are lowercase and the device_id is hexadecimal, without separators.

Supported MQTT Messages

barnowl-mqtt supports raddec messages in either of the following formats:

• JSON string
• CBOR-encoded

The CBOR format results in a slightly reduced message size, at the expense of minor additional computation. It is recommended for network-bandwidth-constrained environments.

Expect other message types to be supported in future versions of barnowl-mqtt.

Is that owl you can do?

While barnowl-mqtt may suffice standalone for simple real-time applications, its functionality can be greatly extended with the following software packages:

• advlib to decode the individual packets into JSON
• barnowl to combine parallel streams of RF decoding data in a technology-and-vendor-agnostic way

These packages and more are bundled together as the Pareto Anywhere open source middleware suite, which includes a variety of barnowl-x listeners, APIs and interactive web apps.

reelyOpinionated

barnowl-mqtt observes reelyActive's JavaScript Style Guide. The npm run lint script uses ESLint and ESLint Stylistic to check the code, flagging any errors and/or warnings. The npm run lint:fix script applies fixes to observe the style guide.

Contributing

Discover how to contribute to this open source project which upholds a standard code of conduct.

Security

Consult our security policy for best practices using this open source software and to report vulnerabilities.

License

MIT License

Copyright (c) 2026 reelyActive

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.