MQTT Debugging

Debug MQTT connections by connecting to an MQTT broker and inspecting publish/subscribe message flow.

Creating an MQTT session

1. Navigate to Realtime in the dashboard
2. Click New Session
3. Select MQTT as the protocol
4. Enter the broker URL (e.g., mqtt://broker.hivemq.com:1883 or wss://broker.hivemq.com:8884/mqtt)
5. Optionally configure:
   • Client ID — unique client identifier
   • Username / Password — broker authentication
   • Clean session — whether to start with a clean session
   • Keep alive — keep-alive interval in seconds
6. Click Connect

Subscribing to topics

Once connected:

1. Enter a topic filter (e.g., sensors/#, home/+/temperature)
2. Select the QoS level (0, 1, or 2)
3. Click Subscribe

Messages matching your subscriptions appear in the message stream.

Inspecting messages

The dashboard displays MQTT messages:

• Topic — the MQTT topic the message was published on
• Payload — message content (JSON is syntax-highlighted)
• QoS — quality of service level
• Retain — whether the message is retained
• Direction — published (outgoing) or received (incoming)
• Timestamp — when the message was sent or received

Publishing messages

Send test messages to the broker:

1. Enter the topic (e.g., sensors/temperature)
2. Enter the payload
3. Select QoS level and retain flag
4. Click Publish

Use cases

• IoT development — debug device-to-cloud messaging
• Broker testing — verify topic routing and QoS behavior
• Integration debugging — inspect messages between services
• Topic design — validate topic hierarchy and wildcard subscriptions