Overview

The IoT platform supports bidirectional communications. Devices can report data to the platform through APIs on the device side, and the platform can push the data to applications by using the subscription/push mechanism or forward the data to other Huawei Cloud services. Devices can also be remotely controlled by means of command delivery (using APIs or the IoTDA console).

Data communications can be upstream or downstream. Upstream data communications include property and message reporting. Downstream data communications include command, message, and property delivery. Properties and commands are defined in product models. If you do not need to use a product model, you can use upstream and downstream messages.

**Table 1** Data communications description
Data Type	Message Type	Differences	Similarities
Upstream data	Property reporting	Dependent on the product model. The properties reported must match those defined in the product model. You can view the latest device shadow on the device details page of the IoTDA console, push the data to the subscribed-to applications, and view historical data through IoT Analytics.	Both properties and messages can be reported to the platform by calling device-side APIs, and forwarded to other Huawei Cloud services using rules.
Upstream data	Message reporting	Independent from the product model. The platform does not verify the message content. The latest reported device shadow data cannot be viewed on the device details page of the IoTDA console. Historical data cannot be viewed through IoT Analytics.
Downstream data	Command delivery	Dependent on the product model. The commands delivered must match those defined in the product model. The command delivery is synchronous. (After a command is delivered, the platform waits for a response from the device. If no response is returned, the command delivery times out.) Commands can be delivered on the IoTDA console.	Commands, properties, and messages can be delivered by calling application-side APIs.
	Property delivery (for modification purposes)	Dependent on the product model. The properties delivered must match those defined in the product model. Property delivery is synchronous. (After a property is delivered, the platform waits for a response from the device. If no response is returned, the modification times out.) The platform supports property configuration (device shadow) on the IoTDA console. Device properties can be modified through the device shadow.
	Message delivery	Independent from the product model. The platform delivers messages to the device. Message delivery is asynchronous. (After a message is delivered, the platform does not need to wait for a response from the device.) Messages can be delivered from the IoTDA console.