Check :example:`bluetooth` folder in ESP-IDF examples, which contains the following demos and their tutorials:
This is a GATT client demo and its tutorial. This demo can scan for devices, connect to the GATT server and discover its services.
This is a multiple connection demo and its tutorial. This demo can connect to multiple GATT server devices and discover their services.
This is a BLE SPP-Like demo. This demo, which acts as a GATT client, can receive data from UART and then send the data to the peer device automatically.