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	Used by a device to report a message
Device messages	$oc/devices/{device_id}/sys/messages/down	Platform	Device	Used by the platform to deliver a message to a device
Device commands	$oc/devices/{device_id}/sys/commands/request_id={request_id}	Platform	Device	Used by the platform to deliver a command to a device
Device commands	$oc/devices/{device_id}/sys/commands/response/request_id={request_id}	Device	Platform	Used by a device to return a command response
Device properties	$oc/devices/{device_id}/sys/properties/report	Device	Platform	Used by a device to report property data
	$oc/devices/{device_id}/sys/gateway/sub_devices/properties/report	Device	Platform	Used by a gateway to report property data in batches
	$oc/devices/{device_id}/sys/properties/set/request_id={request_id}	Platform	Device	Used by the platform to set device properties
	$oc/devices/{device_id}/sys/properties/set/response/request_id={request_id}	Device	Platform	Used by a device to return a response for property setting
	$oc/devices/{device_id}/sys/properties/get/request_id={request_id}	Platform	Device	Used by the platform to query device properties
	$oc/devices/{device_id}/sys/properties/get/response/request_id={request_id}	Device	Platform	Used by a device to return a response for a property query. The response does not affect device properties and shadows.
	$oc/devices/{device_id}/sys/shadow/get/request_id={request_id}	Device	Platform	Used by a device to query device shadow data from the platform
	$oc/devices/{device_id}/sys/shadow/get/response/request_id={request_id}	Platform	Device	Used by the platform to return a response to a device's query of device shadow data
Device events	$oc/devices/{device_id}/sys/events/up	Device	Platform	Used by a device to report an event
Device events	$oc/devices/{device_id}/sys/events/down	Platform	Device	Used by the platform to deliver an event

{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.