Use the MQTT WebSocket client when you need to prove that a broker endpoint, credential set, topic filter, and payload path work from a real browser runtime.
What to test
Validate the full MQTT path, not just the URL.
A broker can accept TCP connections and still fail at WebSocket path routing, TLS termination, username/password auth, topic authorization, or publish permissions. This page keeps the test loop close to the browser behavior your dashboards and web tools actually use.
- WebSocket URL and TLS certificate
- Client ID, keep alive, username, and password
- Subscribe filters and publish topic names
- QoS, retain flag, message payload, and live broker responses
Production checklist
Run the same checks before sharing an endpoint.
Treat every broker URL as an integration contract. Verify authentication, authorization, topic naming, payload shape, and disconnect behavior before adding the endpoint to documentation or device firmware.
- Use a unique client ID per browser session
- Subscribe before publishing test messages
- Keep demo topics away from production namespaces
- Confirm retained messages cannot leak sensitive state
Common failures
Most MQTT WebSocket failures are configuration issues.
When the browser cannot connect, the root cause is often the WebSocket path, CORS-adjacent proxy behavior, certificate mismatch, broker listener configuration, or policy denial rather than MQTT itself.
- Wrong path such as `/mqtt` vs `/ws`
- TLS certificate name mismatch
- Broker listener does not enable WebSocket
- Credentials connect but topic ACL blocks subscribe or publish