{{tag>[linux serial console bluetooth]}}

=====Serial console over Bluetooth=====

====Notes====
  * The rfcomm process has higher CPU usage when connected.
  * The rfcomm utility is deprecated since Bluez 5.44. No alternative found yet, maybe look into PAN.

====Configure====

===Server===
  * Stop ModemManager from interefering:<code>systemctl stop ModemManager
systemctl disable MomdemManager</code>
  * Modify ''/etc/bluetooth/main.conf'':<code>
[Policy]
AutoEnable=true
</code>
  * Start and enable bluetooth service:<code>systemctl enable bluetooth
systemctl start bluetooth</code>
  * Create systemd service ''/etc/systemd/system/rfcomm.service''<code>
[Unit]
Description=RFCOMM service
After=bluetooth.service
Requires=bluetooth.service

[Service]
ExecStart=/usr/bin/rfcomm watch hci0 1 setsid /sbin/agetty --8bits --noclear -L rfcomm0 115200 linux

[Install]
WantedBy=multi-user.target
</code>
  * Enable and start the rfcomm service:<code>systemctl enable rfcomm
systemctl start rfcomm</code>

===Client===
  * Stop ModemManager from interefering:<code>systemctl stop ModemManager
systemctl disable MomdemManager</code>
  * Add user to ''dialout'' group.

===Pairing and connecting===
  * On the server side:<code>bluetoothctl
  discoverable on
  pairable on</code>
  * On the client side:<code>bluetoothctl
  scan on
  -wait to discover server-
  scan off
  pair <mac></code>
  * On the server:<code>bluetoothctl
  discoverable off
  pairable off
  trust <BT-MAC of client></code>
 
  * Connect to the serial console over bluetooth:<code>
# There should be a rfcomm0 device
crw-rw----. 1 root dialout 216, 0 11 jun 08:14 /dev/rfcomm0

# If device is nonexistent, create one
sudo rfcomm connect /dev/rfcomm0 <BT server-MAC-address> 1 &
Connected /dev/rfcomm0 to <MAC> on channel 1
Press CTRL-C for hangup

# Connect to the serial console:
screen /dev/rfcomm0 115200</code>
===Troubleshooting===
  * After resizing your terminal, run: ''resize''.
  * Check bluetooth is not disabled:<code>rfkill list</code>