Topics

When a device connects to IoTDA through MQTT, topics are used in their communication. The following table lists the preset topics in IoTDA.

Category	Topic	Publisher	Subscriber	Function
Device messages	$oc/devices/{device_id}/sys/messages/up	Device	Platform	Device Reporting a Message
Device messages	$oc/devices/{device_id}/sys/messages/down	Platform	Device	Platform Delivering a Message
Device commands	$oc/devices/{device_id}/sys/commands/request_id={request_id}	Platform	Device	Platform Delivering a Command
Device commands	$oc/devices/{device_id}/sys/commands/response/request_id={request_id}	Device	Platform	Example Upstream Response
Device properties	$oc/devices/{device_id}/sys/properties/report	Device	Platform	Device Reporting Properties
	$oc/devices/{device_id}/sys/gateway/sub_devices/properties/report	Device	Platform	Gateway Reporting Device Properties in Batches
	$oc/devices/{device_id}/sys/properties/set/request_id={request_id}	Platform	Device	Platform Setting Device Properties
	$oc/devices/{device_id}/sys/properties/set/response/request_id={request_id}	Device	Platform	Example Upstream Response
	$oc/devices/{device_id}/sys/properties/get/request_id={request_id}	Platform	Device	Platform Querying Device Properties
	$oc/devices/{device_id}/sys/properties/get/response/request_id={request_id}	Device	Platform	Example Upstream Response
	$oc/devices/{device_id}/sys/shadow/get/request_id={request_id}	Device	Platform	Device Obtaining Device Shadow Data from the Platform
	$oc/devices/{device_id}/sys/shadow/get/response/request_id={request_id}	Platform	Device	Example Downstream Response
Device events	$oc/devices/{device_id}/sys/events/up	Device	Platform	Gateway and Child Device Management, Software and Firmware Upgrade, File Upload and Download, Device Time Synchronization, Device Reporting Information, Device Log Collection, and Remote Configuration
Device events	$oc/devices/{device_id}/sys/events/down	Platform	Device

{device_id} identifies the target device that messages with a specific topic will be routed to. When a device subscribes to a topic or pushes messages to a topic, the value of this parameter must be replaced with the device ID used for establishing an MQTT connection between the device and the platform.
{request_id} is used to uniquely identify a request. If this parameter is carried in a message sent by a device, ensure that the parameter value is unique on the device by using an incremental number or UUID. request_id in the response returned by the device must be the same as that contained in the topic received by the device from IoTDA.
When a device subscribes to a topic with the {request_id} parameter, the parameter can be replaced with the number sign (#). For example, when a device subscribes to the command delivery topic $oc/devices/{device_id}/sys/commands/request_id={request_id}, the topic can be specified as $oc/devices/{device_id}/sys/commands/#.
IoTDA uses implicit subscription. Devices do not need to subscribe to the downstream system topic. Devices subscribe to the system topic whose QoS is 0 by default. If the downstream system topic whose QoS is 1 is required, devices need to be configured to subscribe to the topic.
Except device_id and request_id, other fields are system fields.