[BRLTTY] Connection to b':0' failed. Is BRLTTY really running?

[Finn Pedersen]

Dear fellow brl friends,

I have written a small game in python on a raspberry pi and it works
just fine with a Focus Blue 40 (4th gen) from Freedom Scientific, but
when I run the same program with these newer braille displays it fails
to connect.

- Brailliant BI 20X and 40X
- BrailleNote Touch
- APH Mantis Q40
- Focus Blue 40 (5th generation)

I connect to the devices with a USB cable.

It is the brlapi.Connection() that fails.

My error handling gives this response on the Raspberry Pi.

Connection failed: Connection to b':0' failed. Is BRLTTY really running?
error: couldn't connect to b':0' with key
b'keyfile:/etc/brlapi.key+polkit': b'connect: Connection refused'
(brlerrno 11, libcerrno 111, gaierrno 0)


Full program (Python)
https://github.com/finnpedersenkazes/braille-python/blob/main/example03a.py


When no device is connected I get this

File Descriptor: 5
Server Host: b':0'
Authorization Schemes: b'none'
Driver Name: b'NoBraille'

When the Focus Blue 40 (4th gen) is connected I get this

File Descriptor: 3
Server Host: b':0'
Authorization Schemes: b'none'
Driver Name: b'FreedomScientific'
Model Identifier: b'focus40'
Display Width: 40
Display Height: 1


On Ubuntu the message is a bit different. I have checked that there is
a brlapi.key file in the etc folder.

Initialization: Before Connection
Connection failed: Connection to b':0' failed. Is BRLTTY really running?
error: couldn't connect to b':0' with key
b'keyfile:/etc/brlapi.key+polkit': connect: No such file or directory
(brlerrno 11, libcerrno 2, gaierrno 0)
Is BRLTTY really running?
error.brlerrno: 11
error.libcerrno: 2


When I Google for 'keyfile:/etc/brlapi.key+polkit', I am pointed in
the direction of the brltty.conf file in the etc folder.
I must admit that I have no idea what polkit is or what to do about
it. I have looked at the brltty.conf file.
I have located this line and I have tried to uncomment it. It does not
solve the problem.

#api-parameters Auth=keyfile:/etc/brlapi.key # Require authentication key

There is a brlapi.key file in the /etc folder.

I doubt it is my program or the devices that is the problem.
I suspect that there is some aspect of the BRLTTY configuration that I
don't understand.
I also suspected the USB cable, but I have tried different cables with
the same result.
I should be running on the latest versions of everything. Ubuntu
22.04. Python 3.10.6

Any advice or help will be appreciated.

Kind regards,
Finn Pedersen