[Bluez]2.How to use the bluez and hcitool

1 setup bluetooth service

Start the bluetooth service and enable automatic startup, assuming you're using systemd as the init daemon:

sudo systemctl start bluetooth.service
sudo systemctl enable bluetooth.service

2 hcitool scan for bluetooth devices

Before start scanning make sure that your bluetooth device is turned on and not blocked, you can check that with the rfkill command:

sudo rfkill list

If the bluetooth device is blocked (soft or hard blocked), unblock it with the rfkill command again:

sudo rfkill unblock bluetooth

Bring up the bluetooth device with hciconfig command and start scanning, make sure the target device's bluetooth is on and It's discoverable:

sudo hciconfig hci0 up
hcitool scan

Wait few moment to complete the hcitool scan or hcitool lescan

note: use  hcitool lescan  will forever scan ble devices, if use ctrl+c stop it, it will show error

3 bluetooth service discovery

Now we have the bluetooth MAC address of the target device, use the  sdptool  command to know which services (like DUN, Handsfree audio) are available on that target device.

sdptool browse 28:ED:6A:A0:26:B7

You can also use the interactive  bluetoothctl  tool for this purpose.