Connection

• Host: use the broker host shown on the device's Connection details card. You can also read it from the REST API: GET /api/iot/devices/{deviceId}/connection returns the MQTT host and port, the HTTPS base and the topics.
• Port: use 8883 (TLS).
  • Plain port 1883 works only if the device profile turns on Plain MQTT.
  • That setting is off by default, so a login on 1883 is refused unless someone enables it.
• Protocol: MQTT 3.1.1. An MQTT 5 CONNECT is refused with CONNACK 1.
• Session settings: send clean session = true and use MQTT keepalive.
• TLS:
  • TLS 1.2 minimum, 1.3 preferred.
  • SNI is required, so connect by host name, not by IP address.
  • Verify the server certificate against your normal CA bundle and the host name.
  • Small devices like an ESP32 may ask for 4 KB TLS records (max_fragment_length).

Credentials (access token, the default login)

• Client ID: any valid ID: 1–64 characters from A–Z a–z 0–9 . _ : -
• Username: the device access token
• Password: empty

A CONNECT without a username is refused. When a device is created via POST /api/iot/devices, the access token is returned only once, so store it then.

Topic

Publish telemetry to v1/telemetry. Anything else under v1/ that isn't a known topic is rejected. Three rejected topics in a minute close the session.

Payload

Any of these forms works:

• A flat object:

{"temperature": 21.5, "humidity": 40}

• An object with a timestamp in milliseconds:

{"ts": 1759572000000, "values": {"temperature": 21.5, "humidity": 40}}

• An array of either form.

If the connection is refused

• 4 (bad username or password): Back off for at least 5 minutes
• 5 (not authorised): Back off with the long schedule

The reason behind code 5 is not sent to the device. It is written to the device's Log.

Sources

• MQTT
• Device HTTP API
• Device profiles
• REST API basics

Written by AI from the documentation and solved topics. If it solved your problem, mark it as the solution; if not, the team will follow up.