Platform Querying Device Properties

Function

This API is used by the platform to query property information from a device. For details of the API, see Query Device Properties. When a device receives a property query request, the device needs to return its property data to the platform. Otherwise, the request is considered to have timed out by the platform.

It is not suitable to report data in JSON format for devices with low configuration and limited resources or with limits on bandwidth usage. In this case, devices can transparently transmit the original binary data to the platform, but a codec is required to convert binary data to JSON format. For details about how to develop codecs, see Developing a Codec.

Topic

Downstream: $oc/devices/{device_id}/sys/properties/get/request_id={request_id}

Upstream: $oc/devices/{device_id}/sys/properties/get/response/request_id={request_id}

• {request_id} is used to uniquely identify a request. If a device receives a downstream request with a topic carrying a request ID, the request ID must be included in the topic of the upstream response returned by the device.
• When an application queries device properties, the platform generates a unique ID to identify the request. This ID is carried in request_id in the downstream topic of the platform-side device property query.
• The device cannot detect the request_id in advance. When a device subscribes to a topic that ends with request_id={request_id}, the number sign (#) can be used to replaced request_id={request_id}, for example, $oc/devices/{device_id}/sys/properties/get/#.

Downstream Request Parameters

Upstream Response Parameters

ServiceProperty structure

Example Downstream Request

Topic: $oc/devices/{device_id}/sys/properties/get/request_id={request_id} 
Data format:
{
    "object_device_id": "{object_device_id}"
    "service_id": "Temperature"
}

Example Upstream Response

Topic: $oc/devices/{device_id}/sys/properties/get/response/request_id={request_id}
Data format:
{
    "services": [
        {
            "service_id": "Temperature",
            "properties": {
                "PhV_phsA": "1",
                "PhV_phsB": "2"
            },
            "event_time": "20190606T121212Z"
        }
    ]
}