Solution maturity

[x48x4b]

Please see also my recent not resolved discussion #805 here.

According to my recent experienced it is far from straightforward to get "bumble" to bridge between an android emulator an a fairly common usb bluetooth dongle (ASUS BT400).

This is in sharp contrast e.g. to a Win10 virtual instance in VirtualBox.
A few clicks and the virtual machine is connected to my bluetooth dongle and then successfully pairs with my bluetooth device.

The very least would be a list of known working bluetooth dongles with Bumble.
(sorry if I missed to find it.)

[barbibulle]

This BT400 dongle likely requires a driver (which is why it doesn't present itself as a regular Bluetooth class USB device). This is also why it works with a windows guest in virtualbox, because in that case the windows driver will deal with it. Here, with the Android emulator, you don't have a dongle-specific driver. Bumble does have support for some vendor-specific drivers (Realtek and Intel), but not the (quite old by now) Asus BT400. The Asus BT500 works well (Realtek chip). We don't have an official list of USB dongles at this point. Would be a nice crowdsourced contribution.

[x48x4b]

Today I received my BT500 but it does not pair either:

./emulator -avd Medium_Phone_API_36.1 -accel auto -gpu auto

---

$ bumble-hci-bridge android-netsim:_:8554,mode=controller usb:0

connecting to HCI...
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1761832428.032040 8127 chttp2_server.cc:712] WARNING: UNKNOWN:Only 1 addresses added out of total 2 resolved {children:[UNKNOWN:Unable to configure socket {children:[UNKNOWN:bind: Address already in use (98)]}]}
connected
connecting to HCI...
connected
14:53:55.606 I bumble.bridge: [CONTROLLER->HOST] HCI_INQUIRY_COMPLETE_EVENT:
status: HCI_SUCCESS
14:54:05.925 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_REQUEST_EVENT:
bd_addr: 5C:FB:7C:63:21:DF/P
class_of_device: 2360324
link_type: ACL
14:54:20.987 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_COMPLETE_EVENT:
status: HCI_CONNECTION_TERMINATED_BY_LOCAL_HOST_ERROR
connection_handle: 1
bd_addr: 5C:FB:7C:63:21:DF/P
link_type: ACL
encryption_enabled: 0
14:54:25.365 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_REQUEST_EVENT:
bd_addr: 5C:FB:7C:63:21:DF/P
class_of_device: 2360324
link_type: ACL
14:54:40.427 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_COMPLETE_EVENT:
status: HCI_CONNECTION_TERMINATED_BY_LOCAL_HOST_ERROR
connection_handle: 1
bd_addr: 5C:FB:7C:63:21:DF/P
link_type: ACL
encryption_enabled: 0

[zxzxwu]

Bumble HCI bridge simply forward everything. Once you can see packets are forwarded, you need to check logcat and snoop log of Android Bluetooth stack to see what's happened.

[barbibulle]

The Asus BT-500 dongle has a Realtek chip, so it is recommended downloading a recent FW image that can get loaded after boot.
See https://google.github.io/bumble/drivers/realtek.html for details

[x48x4b]

Thank you for the hint. I loaded the rtk driver, see below.
At the end of today, I would like to pair my emulator phone with my bluetooth hardware, a HC05 serial to bluetooth converter.
I simply want to develop some app for that use case.
But I have not achieved this pairing so far, despite using a BT500 and loading the rtk firmware ...
Also, I do not know how to "to check logcat and snoop log of Android Bluetooth stack".

$ export BUMBLE_RTK_FIRMWARE_DIR=/home/someuser/.local/share/bumble/firmware/realtek
someuser@somehost:$ echo $BUMBLE_RTK_FIRMWARE_DIR
/home/someuser/.local/share/bumble/firmware/realtek
someuser@somehost:$ bumble-hci-bridge android-netsim:_:8554,mode=controller usb:[driver=rtk]0

connecting to HCI...
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1761844255.388324 13005 chttp2_server.cc:712] WARNING: UNKNOWN:Only 1 addresses added out of total 2 resolved {children:[UNKNOWN:Unable to configure socket {children:[UNKNOWN:bind: Address already in use (98)]}]}
connected
connecting to HCI...
connected

18:11:19.787 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_REQUEST_EVENT:
bd_addr: 5C:FB:7C:63:21:DF/P
class_of_device: 2360324
link_type: ACL
18:11:34.849 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_COMPLETE_EVENT:
status: HCI_CONNECTION_TERMINATED_BY_LOCAL_HOST_ERROR
connection_handle: 1
bd_addr: 5C:FB:7C:63:21:DF/P
link_type: ACL
encryption_enabled: 0

[x48x4b]

I just wonder if there is a known working scenario with Linux that connected a realtek based bluetooth dongle with an android phone emulator. Details would be interesting to know.

It seems to me that #690 ("open") describes almost the same problems I encountered.

[barbibulle]

I'll try to reproduce and investigate. Maybe something odd is going on with recent versions of the Android emulator.

[x48x4b]

Meanwhile I did the following experiment (partial command line output see below).

1. Started emulator, says "Activated packet streamer for bluetooth emulation".
2. Started traffic monitor on relevant port (tcpdump).
3. Started bridge and treid to pair my bluetooth headphones.
4. Result:

• bumble-hci-bridge outputs communication with bluetooth dongle
• no traffic on relevant port seen by tcpdump.

Do I miss something?

========================
partial command line output

Emulator

someuser@somehost:/Android/Sdk/emulator$ uname -a ; date
Linux somehost 6.17.6-200.fc42.x86_64 #1 SMP PREEMPT_DYNAMIC Wed Oct 29 18:58:05 UTC 2025 x86_64 GNU/Linux
Di 04 Nov 2025 13:42:46 CET
someuser@somehost:/Android/Sdk/emulator$ ./emulator -packet-streamer-endpoint default -avd Pixel_6a -accel auto -gpu auto -no-snapshot-load
...
INFO | Activated packet streamer for uwb emulation
INFO | Activated packet streamer for bluetooth emulation

Traffic

someuser@somehost:~/Android/Sdk/emulator$ sudo tcpdump -v -i lo port 8554
dropped privs to tcpdump
tcpdump: listening on lo, link-type EN10MB (Ethernet), snapshot length 262144 bytes

Bridge

someuser@somehost:/Android/Sdk/emulator$ export BUMBLE_RTK_FIRMWARE_DIR=/home/someuser/.local/share/bumble/firmware/realtek
someuser@somehost:/Android/Sdk/emulator$ bumble-hci-bridge android-netsim:_:8554,mode=controller usb:[driver=rtk]0

connecting to HCI...
WARNING: All log messages before absl::InitializeLog() is called are written to STDERR
I0000 00:00:1762260343.513903 7650 chttp2_server.cc:712] WARNING: UNKNOWN:Only 1 addresses added out of total 2 resolved {children:[UNKNOWN:Unable to configure socket {children:[UNKNOWN:bind: Address already in use (98)]}]}
connected
connecting to HCI...
connected
13:45:57.649 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_REQUEST_EVENT:
bd_addr: 5C:FB:7C:63:21:DF/P
class_of_device: 2360324
link_type: ACL
13:46:12.717 I bumble.bridge: [CONTROLLER->HOST] HCI_CONNECTION_COMPLETE_EVENT:
status: HCI_CONNECTION_TERMINATED_BY_LOCAL_HOST_ERROR
connection_handle: 1
bd_addr: 5C:FB:7C:63:21:DF/P
link_type: ACL
encryption_enabled: 0

Ports:

someuser@somehost:~/Android/Sdk/emulator$ nmap 127.0.0.1 -p 0-10000
Starting Nmap 7.92 ( https://nmap.org ) at 2025-11-04 13:45 CET
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00026s latency).
Not shown: 9994 closed tcp ports (conn-refused)
PORT STATE SERVICE
631/tcp open ipp
5037/tcp open unknown
5355/tcp open llmnr
5554/tcp open sgi-esphttp
5555/tcp open freeciv
6402/tcp open boe-eventsrv
8554/tcp open rtsp-alt

Nmap done: 1 IP address (1 host up) scanned in 0.49 seconds