Q1: What should be filled in ClientIdentifier, UserName and UserPassword of the Payload during MQTT connection authentication?
A: ClientIdentifier: Device ID obtained in device creation, i.e. a numeric string;
UserName: Product ID assigned by the platform during product registration, i.e. a numeric string;
UserPassword: Device authentication information (i.e. unique device number, SN) or apiKey, which is a string.
Q2: Does MQTT need to pass connection authentication before sending other messages?
A: Yes. The MQTT protocol must be authenticated (after receiving ConnAck) before sending subsequent messages for interaction. Otherwise, the messages will be discarded directly by the server.
Q3: What are the restrictions over Topic subscription by MQTT?
A: OneNET does not support the subscription of system topics starting with $.
Q4: How to use the MQTT protocol to upload data to the cloud platform?
A: After the connection authentication, package data in a certain format (see the protocol file), and publish data to the $dp system Topic.
Q5: Is it necessary to create a Topic before subscription?
A: When the device executes subscription, OneNET will automatically determine whether the Topic exists. If it does not exist, the Topic will be created automatically.
Q6: Is the data stream information of other devices available through subscription?
A: Yes. The latest data point information of a device can be obtained in time by subscribing the /device_id/data stream name.
Q7: What are the restrictions over message publishing??
A: Messages must be published under the same product ID, and cannot be published among products.