// mqtt

MQTT

Connect to an MQTT broker over a persistent backend connection, subscribe to topics, and publish messages — all from a request tab, with a live transcript of the traffic.

What It Does

  • Connects to plaintext (mqtt://, default port 1883), TLS (mqtts://, default port 8883), or bare host:port brokers
  • Subscribes to a topic, including wildcards like sensors/#
  • Publishes messages to a topic
  • Supports QoS 0, 1, and 2 for the subscription and published messages
  • Optional client ID (auto-generated when blank), username, and password
  • Resolves {{variables}} in topics, client ID, credentials, and payload
  • Keeps the password in the OS keychain — it is not written to the collection files or the saved tab state
  • Live status indicator with a received-message count and an incoming-message flash
  • Transcript of published and received messages with topics and timestamps

Connecting

  1. Enter the broker URL — mqtt://broker.example.com, mqtts://… for TLS, or host:port
  2. Optionally set a client ID, username, and password
  3. Click Send — the status indicator goes live once connected. Sending again with the same settings reuses the open connection
  4. Use the Disconnect button in the MQTT panel to close the connection

Subscribing

  1. Enter a topic filter, e.g. sensors/temperature or sensors/# for a wildcard
  2. Choose the QoS level
  3. Click Send — matching messages stream into the transcript as they arrive

Publishing

  1. Enter the target topic
  2. Enter the payload in the body editor
  3. Click Send — the message is published on the open connection

Troubleshooting

Cannot connect

  • Check the scheme and port — 1883 for mqtt://, 8883 for mqtts://
  • Verify credentials, and that the broker accepts your client ID

No messages received

  • Confirm the topic filter actually matches the published topics
  • Check that the subscription QoS is acceptable to the broker

Next Steps