Check bluetooth/bluedroid/classic_bt folder in ESP-IDF examples, which contains the following application:
- This is a BT_L2CAP demo. This demo can connect, send and receive L2CAP data
bluetooth/bluedroid/classic_bt/bt_l2cap_client,bluetooth/bluedroid/classic_bt/bt_l2cap_server
inc/esp_l2cap_bt_api.inc