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Can't get web service to work with no screen plugged in
Posted: Sun Oct 20, 2019 9:37 am
by smadds
I'm using the latest RPi img download onto a Pi 2b. I just want to use it with web remote control, but without a screen plugged in I cannot access the device on port 9999.
SSH works fine, and if I try to run the "sudo qlcplus" from the command line I get the following error:
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sudo qlcplus
qt.qpa.screen: QXcbConnection: Could not connect to display
Could not connect to any X display.
Any ideas?
Re: Can't get web service to work with no screen plugged in
Posted: Sun Oct 20, 2019 9:41 am
by smadds
Also, service status if its any help:
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sudo service qlcplus status
● qlcplus.service - LSB: Q Light Controller Plus
Loaded: loaded (/etc/init.d/qlcplus; generated)
Active: active (exited) since Sat 2019-10-19 18:42:35 BST; 15h ago
Docs: man:systemd-sysv-generator(8)
Process: 334 ExecStart=/etc/init.d/qlcplus start (code=exited, status=0/SUCCESS)
Oct 19 18:42:35 rpi-wc-lights systemd[1]: Starting LSB: Q Light Controller Plus...
Oct 19 18:42:35 rpi-wc-lights qlcplus[334]: Starting Q Light Controller Plus: qlcplus.
Oct 19 18:42:35 rpi-wc-lights systemd[1]: Started LSB: Q Light Controller Plus.
Re: Can't get web service to work with no screen plugged in
Posted: Sun Oct 20, 2019 4:04 pm
by Uncle
Please see this thread. It is a know issue and can be solved by editing config.txt
viewtopic.php?t=13738
Re: Can't get web service to work with no screen plugged in
Posted: Tue Oct 22, 2019 9:10 am
by smadds
Thank you so much for taking the time to reply, Eric. That worked perfectly.
Maybe something could be added to the RPi documentation to highlight this to others wanting to use one without a monitor? Something like:
WARNING - Monitor needed
If you plan to use your RPi without a monitor, QLC+ will not be able to run unless you make a configuration change to the RPi.
To do this, first SSH into the device (e.g. using Putty, default user: pi password: raspberry), then edit the config file (sudo nano /boot/config.txt). Add the following on a new line at the bottom of the file:
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# Allow booting without monitor
hdmi_force_hotplug=1
Save the file (ctl o, enter, ctl x) then reboot (sudo reboot now). Et voila - QLC+ will be running and you'll be able to access it on port 9999 via a browser.
Re: Can't get web service to work with no screen plugged in
Posted: Wed Sep 09, 2020 12:23 pm
by interact
I've had the same problem as the original poster, but on a HummingBoard2. After trying a lot of things, I found that setting a environment variable with "export QT_QPA_PLATFORM='offscreen' " did the trick. Maybe this also works for a Pi...
Re: Can't get web service to work with no screen plugged in
Posted: Mon Nov 16, 2020 5:15 pm
by MDAR
Maybe I'm lazy, but I just plugged in a £5 4K HDMI dummy plug.