Check 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.
bluetooth/gatt_client- :example_file:`GATT Client Example Walkthrough <bluetooth/gatt_client/tutorial/Gatt_Client_Example_Walkthrough.md>`
This is a multiple connection demo and its tutorial. This demo can connect to multiple GATT server devices and discover their services.
bluetooth/gattc_multi_connect- :example_file:`GATT Client Multi-connection Example Walkthrough <bluetooth/gattc_multi_connect/tutorial/Gatt_Client_Multi_Connection_Example_Walkthrough.md>`
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.
bluetooth/ble_spp_client