Help Center/ IoT/ API Reference/ MQTT Interface Reference/ Overview/ Message Format
Updated on 2022-02-24 GMT+08:00
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Message Format

An MQTT message consists of fixed header, variable header, and payload.

For details about the format of fixed header and variable header, see MQTT Version V3.1.1. Payload is defined by the application in the PUBLISH (PUB) message, that is, by the device and the IoT platform.

The following describes the CONNECT, SUBSCRIBE, and PUBLISH messages.

  • CONNECT - Client requests a connection to a server

    For details about the parameters in the payload of a CONNECT message, see MQTT Connection Authentication Through CONNECT Messages.

  • SUBSCRIBE - Subscribe to named topics

    Set Topic name in the payload to the topic that a device wants to subscribe to. Currently, the value of this parameter is the topic of the device. For details, see Topic Definition.

  • PUBLISH - Publish message
    • The value of Topic name in the variable header is the topic of the IoT platform when the device sends a message to the IoT platform. When the device receives a message from the IoT platform, the value of Topic name is the topic of the device. For details, see Topic Definition.
    • The content in the payload is a complete data reporting message or command delivery message. Currently, it is a JSON object.
Parent topic: Overview