"/dev/tty" problem when launching a game NOT using Emulationstation.

[djaay]

So i am hacking a bit. Playing around with the system. Mostly just to learn about Linux/RetroPie.

I built a node server that is auto started at boot with this line in rc.local
su pi -c 'node /home/pi/devtest/main.js < /dev/null &'

Then after all is booted and finished i execute a shell script with my node server...this line:
/opt/retropie/supplementary/runcommand/runcommand.sh 0 SYS nes /home/pi/RetroPie/roms/nes/Airwolf.nes

Nothing happens. But when i close Emulationstation i see "Unable to open tty". And some line errors from the runcommand.sh (that is unchanged).

You can see what i am trying to do. I am trying to launch a game without selecting it from Emulationstation. I am trying to simulate that i selected a game from within Emulationstation. I can see that runcommand.sh does some fancy menu hiding and such. So i wanted to use runcommand.sh instead of just running retroarch myself from CLI.

But the problem is the "tty" stuff. Is it because i don´t have the rights to tty? Is it because of my startup line
su pi -c 'node /home/pi/devtest/main.js < /dev/null &'?

I´m really stuck here.

NOTE: Everything is running just as normal. The only difference is my server that lays in the background trying to execute some commands.

Thankful for any help!