Disconnected: D8:F8:83:9F:72:1A (public) (reason 19) on ncs v2.4.2

[snowuyl]

I write an Windows 11 APP to pair and send data to nRF52832 DK through Nordic UART Service (NUS). But RTT Viewer shows "Disconnected: D8:F8:83:9F:72:1A (public) (reason 19)". What is meaning of reason 19 and how to fix this issue?

00> *** Booting Zephyr OS build v3.3.99-ncs1-1 ***
00> [00:00:00.000,579] <inf> bt_sdc_hci_driver: SoftDevice Controller build revision: 
00>                                             e0 7e 2e c1 5e 05 85 23  46 15 dc fa 8e 29 7d 70 |.~..^..# F....)}p
00>                                             10 93 a5 fc                                      |....             
00> [00:00:00.003,082] <inf> bt_hci_core: HW Platform: Nordic Semiconductor (0x0002)
00> [00:00:00.003,112] <inf> bt_hci_core: HW Variant: nRF52x (0x0002)
00> [00:00:00.003,143] <inf> bt_hci_core: Firmware: Standard Bluetooth controller (0x00) Version 224.11902 Build 2231721665
00> [00:00:00.004,302] <inf> bt_hci_core: Identity: C4:4D:87:46:02:3A (random)
00> [00:00:00.004,364] <inf> bt_hci_core: HCI: version 5.4 (0x0d) revision 0x1077, manufacturer 0x0059
00> [00:00:00.004,394] <inf> bt_hci_core: LMP: version 5.4 (0x0d) subver 0x1077
00> [00:00:00.004,394] <inf> bt: Bluetooth initialized
00> connected() e
00> Connected D8:F8:83:9F:72:1A (public)
00> btInfo.le.interval=36
00> btInfo.le.latency=0
00> btInfo.le.timeout=42
00> _gCurrentConn=0x20001f08
00> bt_conn_le_data_len_update() ok
00> state = connect
00> btNusThreadCreate() e
00> connected() x
00> [00:00:31.226,165] <inf> bt: Data length updated. Length 251/251 bytes, time 2120/2120 us
00> [00:00:33.161,193] <inf> bt: Pairing completed: D8:F8:83:9F:72:1A (public), bonded: 0
00> [00:00:33.161,437] <inf> bt: Security changed: D8:F8:83:9F:72:1A (public) level 4
00> state = disconnect
00> btNusThreadAbort() e
00> Disconnected: D8:F8:83:9F:72:1A (public) (reason 19)

[Simonr]

Hi

Disconnect reason 19 means that the remote user terminated the connection, meaning the other side of this connection. So if this is the log you're seeing on the nRF side it means the Windows application is causing the disconnect. Perhaps because it doesn't support the security level or one or more of the services/characteristics you're trying to read/write to/from? 

We will need a log of the Windows application you're using to see why these disconnects occur. A list of disconnects can be found here for future reference: https://github.com/nrfconnect/sdk-zephyr/blob/v3.4.99-ncs1/include/zephyr/bluetooth/hci_types.h#L3011-L3080. Note that they are in hexadecimal values, so reason 19 equals to 0x13 in the disconnect reason list.

Best regards,

Simon