I've spent years working with embedded systems, IoT devices, MQTT brokers and network infrastructure. One recurring frustration is trying to work out why an MQTT connection isn't working.

A device might successfully establish TCP, then fail TLS negotiation, hit an incorrect WebSocket endpoint, or get rejected during MQTT CONNECT. Those failures can look similar from the application side, but require very different fixes.

I built MQTT Doctor to make that diagnosis more systematic.

It's a Windows desktop tool that checks DNS, TCP, TLS, WebSocket upgrades, MQTT 3.1.1/5.0 connection responses and keepalive behaviour, then explains the evidence and suggests what to investigate next.

The Professional edition adds live topic monitoring, connection health testing, endpoint comparisons, subscription permission checks and diagnostic reports.

There's a free Community Edition available to try, and everything runs locally without telemetry or a cloud account.

A deliberate design decision was to distinguish observed failures from possible causes. For example, a TCP timeout shouldn't automatically be reported as a firewall fault.

I've spent years working with embedded systems, IoT devices, MQTT brokers and network infrastructure. One recurring frustration is trying to work out why an MQTT connection isn't working.

I built MQTT Doctor to make that diagnosis more systematic.

The Professional edition adds live topic monitoring, connection health testing, endpoint comparisons, subscription permission checks and diagnostic reports.

There's a free Community Edition available to try, and everything runs locally without telemetry or a cloud account.

A deliberate design decision was to distinguish observed failures from possible causes. For example, a TCP timeout shouldn't automatically be reported as a firewall fault.

MQTT Doctor

Stop guessing. Start diagnosing.

Stop guessing. Start diagnosing.