MQTT.fx

The tool provides a graphical environment for connecting to MQTT brokers and exercising IoT communication flows without writing code. Users can create reusable connection profiles that store broker address, port, client identifier, MQTT version, and security settings, then subscribe to topics, publish messages, and observe traffic in real time. A built‑in topic explorer discovers active and retained topics, presenting them in an alphabetically sorted list for quick subscription or export.

A range of payload decoders is bundled, including plain text, JSON, Base64, hex, binary, Msgpack, and Sparkplug formats, and the application exposes an interface for adding custom decoders. The Sparkplug explorer and editor let users view messages as formatted JSON, construct virtual edge nodes, and assemble payloads with metrics and properties before publishing.

For more advanced scenarios, the software supports scripted messaging using a GraalVM JavaScript engine, enabling automated publishing and receiving sequences. It targets developers, IoT engineers, and hobbyists who need to validate broker configurations and message payloads during development or production monitoring.