After introducing how to discover devices in the LAN, this section will introduce how to control the devices. Taking the smart light as an example, the simplest control is to turn the smart light on and off, which is essentially the GPIO pin level being pulled high or low at the software level. Controlling the on and off of the smart light through other devices is nothing more than providing commands to perform GPIO operations. So how are these commands sent from a smartphone to the smart light? What is the format of these commands? What protocols are used? This section will answer these questions one by one. This section mainly introduces the transmission of data conforming to the TCP/IP protocol through Wi-Fi wireless transmission media, and the transmission of data conforming to the Bluetooth data communication protocol through the Bluetooth wireless transmission media.