[BRLTTY] Brlapi not connecting in headless mode

[Julian Dreykorn]

Hi,

using enterTtyModeWithPath instead actually fixed the issue and I thank 
you very much for your good intuition.
It now works mostly as expected in any case on the raspberry pi.
I do get one InterruptedIOException on waitForPacket immediately thrown 
once on the first call of readKeyWithTimeOut.
Although this does not actually affect the program and reading keys is 
not an issue regardless,
this did not happen with just using enterTtyMode.

To not leave the initial problem unclear, I'll detail it out further.
I run my program on the pi after startup, so brltty is already ready.
I expected the program to take control of an attached display, enter 
tty-mode and write something on it.
Connecting and entering tty-mode returned me the correct results. No 
error values and the display was correctly
identified by model, etc. Calling Connection.Write or .ReadKey did not 
return any errors either.
The real display was completely unaffected though and either displayed 
"Screen not in text mode" or the
console (tty0) login screen if the braille display was attached before 
the pi was started up.
I could use the display to navigate a tty, while it was supposed to be 
seized by brlapi.

The one case where it worked correctly for me was when I used the 
graphical user interface of the pi,
so a proper desktop environment with an attached desktop, to log into 
the system, open a pseudo terminal,
and run the program like that.
Finally I should mention that I always entered ttymode on tty0, since 
using default (-1) did not work out for me.

I suppose I haven't properly understood yet how the real display is 
addressed
through the tty it is attached to by brltty.

Again I thank you for the fast replies. I am certainly no longer stuck 
on this main problem now.
Best, Julian

Am 27.03.2025 um 09:41 schrieb Sébastien Hinderer:
> Hello,
>
> My intuition is that libbrlapi is unable to figure out on which tty it is
> running I would suggest to enter in tth mode with enterTtyModeWithPath,
> likely with an empty path to make sure the displayed content will be
> passed to the device in any case.
>
> Please let us know whether this is able to unblock you or not.
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