ref: https://unix.stackexchange.com/posts/92256/timeline
Connect/turn on your bluetooth adapter on Linux. Ensure your adapter is visible (can be set in gnome-bluetooth -- you should see a bluetooth system tray icon).
Add a serial posrt:
sdptool add --channel=22 SP
Now listen on this channel using rfcomm:
sudo rfcomm listen /dev/rfcomm0 22
rfcomm will block, listening for a connection with a message like
Waiting for connection on channel 22
Back on Android:
If hci0 not up
bluebinder
then
hciconfig hci0 up
Finally, if for example PC BT address is: D0:B1:28:94:2D:50 and Android BT address is: D0:B1:28:94:2D:50
rfcomm connect hci0 34:02:86:F9:B3:38 22
You should now get:
Connected /dev/rfcomm0 to 34:02:86:F9:B3:38 on channel 22
Press CTRL-C for hangup