When I tried to use gatttool and bluetoothctl to connect to a bluetooth device, gatttool got "Connection refused" but bluetoothctl connected to it successfully.
What's the difference between bluetoothctl and gatttool?
How to make gatttool work because I need to use char-write-cmd command in gatttool?
$ ./gatttool -b 00:13:04:0C:6C:26 -I
[00:13:04:0C:6C:26][LE]> connect
Attempting to connect to 00:13:04:0C:6C:26
Error: connect error: Connection refused (111)
[00:13:04:0C:6C:26][LE]> exit
$ bluetoothctl
[NEW] Controller B8:27:EB:07:26:C8 raspberrypi [default]
[NEW] Device 00:13:04:0C:6C:26 MEDXING-NIBP
[bluetooth]# connect 00:13:04:0C:6C:26
Attempting to connect to 00:13:04:0C:6C:26
[CHG] Device 00:13:04:0C:6C:26 Connected: yes
Connection successful
[bluetooth]# info 00:13:04:0C:6C:26
Device 00:13:04:0C:6C:26
Name: MEDXING-NIBP
Alias: MEDXING-NIBP
Paired: no
Trusted: no
Blocked: no
Connected: yes
LegacyPairing: no
UUID: Generic Access Profile (00001800-0000-1000-8000-00805f9b34fb)
UUID: Generic Attribute Profile (00001801-0000-1000-8000-00805f9b34fb)
UUID: Device Information (0000180a-0000-1000-8000-00805f9b34fb)
UUID: Unknown (0000ffb0-0000-1000-8000-00805f9b34fb)
[bluetooth]# exit