Sure, btmon trace: (...) > ACL Data RX: Handle 200 flags 0x00 dlen 1033 #32 [hci0] 17.083174 invalid packet size (12 != 1033) 08 00 01 00 02 01 04 00 01 10 ff ff ............ @ MGMT Event: Device Connected (0x000b) plen 13 {0x0002} [hci0] 17.104462 BR/EDR Address: 10:AA:AA:AA:AA:AA (OUI 10-AA-AA) Flags: 0x00000000 Data length: 0 @ MGMT Event: Device Connected (0x000b) plen 13 {0x0001} [hci0] 17.104462 BR/EDR Address: 10:AA:AA:AA:AA:AA (OUI 10-AA-AA) Flags: 0x00000000 Data length: 0 < ACL Data TX: Handle 200 flags 0x02 dlen 16 #33 [hci0] 17.149691 L2CAP: Connection Response (0x03) ident 1 len 8 Destination CID: 64 Source CID: 65535 Result: Connection pending (0x0001) Status: No further information available (0x0000) < ACL Data TX: Handle 200 flags 0x02 dlen 10 #34 [hci0] 17.154828 L2CAP: Information Request (0x0a) ident 2 len 2 Type: Extended features supported (0x0002) > ACL Data RX: Handle 200 flags 0x00 dlen 2061 #35 [hci0] 17.145762 invalid packet size (16 != 2061) 0c 00 01 00 04 01 08 00 40 00 00 00 01 02 00 00 ........@....... > ACL Data RX: Handle 200 flags 0x00 dlen 2061 #36 [hci0] 17.146654 invalid packet size (16 != 2061) 0c 00 01 00 03 01 08 00 00 00 00 00 00 00 00 00 ................ > ACL Data RX: Handle 200 flags 0x00 dlen 2061 #37 [hci0] 17.147190 invalid packet size (16 != 2061) 0c 00 01 00 04 01 08 00 40 00 00 00 05 00 00 00 ........@....... > ACL Data RX: Handle 200 flags 0x00 dlen 1804 #38 [hci0] 17.148090 invalid packet size (15 != 1804) 0b 00 01 00 04 01 07 00 40 00 00 00 05 00 00 ........@...... > ACL Data RX: Handle 200 flags 0x00 dlen 1547 #39 [hci0] 17.148708 invalid packet size (14 != 1547) (...) The last ACL data packet invokes: l2cap_bredr_sig_cmd l2cap_config_rsp l2cap_send_disconn_req l2cap_state_change_and_error Bluetooth: chan 00000000205763be BT_CONFIG -> BT_DISCONN This is the code and whole log: https://gist.github.com/swkim101/82bc694f9427f008c14e91307b3355b6 Thanks.