MQTT.fx User Manual#

MQTT.fx is a desktop client for working with MQTT brokers. It connects to brokers over TCP and TLS, subscribes to and publishes on topics, explores a broker's topic namespace, decodes and edits message payloads, automates traffic with JavaScript, and works with Sparkplug B systems. It supports MQTT 3.1.1 and MQTT 5.0 and runs on macOS, Windows, and Linux.

This manual describes how to use MQTT.fx. It is written and maintained from the MQTT.fx source repository so that it stays grounded in the actual product. You can open it from within the app at any time via Help → User Manual. For the conventions used while authoring it, see DOCS_GUIDE.md.

MQTT.fx is a commercial product by Softblade GmbH. The application can be tried without a license through free Demo Sessions and a free 30‑day trial license. See License and trial.

Getting started#

• Installation — download, install, system requirements.
• Getting started — a quick tour and your first message.
• Your first connection — connect to a broker step by step.

Working with brokers#

• Connection profiles — create, edit, organize, and import/export broker connections.
• Publish and subscribe — send and receive messages, QoS, retained messages, recent-topics history, the message clipboard.
• Namespace Explorer — explore a broker's live topic tree.
• Broker status — monitor $SYS broker statistics.

Protocol and data#

• MQTT 5 features — MQTT 5.0 specific options and message properties.
• Payloads and formatting — payload decoders and editors, formatting, and saving payloads.
• Sparkplug B — the Sparkplug Explorer and Sparkplug Editor.

Security#

• TLS and security — TLS/SSL connection options, certificates, and keystores.
• Authentication — username/password and certificate-based authentication.

Automation and diagnostics#

• Scripting — automate MQTT traffic with JavaScript.
• Logging and debugging — the log viewer and log files.
• Settings — application preferences and options.
• Troubleshooting — common problems and fixes.

Reference#

• License and trial — Demo Sessions, trial, and entering a license.
• Release notes — version history.
• Appendix — file locations, glossary, keyboard shortcuts.