hcitool scan
# 00:11:22:33:44:55
sudo rfcomm bind /dev/rfcomm0 00:11:22:33:44:55
ls -l /dev/rfcomm0
# crw-rw---- root dialout ... /dev/rfcomm0
sudo usermod -a -G dialout
# You should logout/login
For access in VirtualBox guest machine you should enable serial port, select Host Device
and define the path /dev/rfcomm0
in the settings of machine.