Section 9.1 described what remote control was. As the topological structure of remote control shows, the smartphone and the controlled device are not directly connected. They are connected to the cloud server, and the data sent by both are forwarded by the cloud. Then, what is the protocol for connecting the device to the cloud? What is the protocol for data communication? Only by figuring out these protocols can you have a basic understanding of remote control.
At present, common protocols for connecting devices to the cloud are the MQTT protocol and HTTP protocol. This chapter will only cover the former as the latter has been introduced in Chapter 8.