Cannot connect to X server :0.0 with a Qt application

linux qt x11

ant2009 · Mar 15, 2009 · Viewed 96.4k times · Source

Compiling on Fedora 10.

I have just started my first qt GUI application. I used all the default settings.

Its just a simple form. It builds OK without any errors. But when I try and run the application. I get the following message:

Starting /home/rob/projects/qt/test1/test1/test1...
No protocol specified
test1: cannot connect to X server :0.0

Thanks for any advice,

Answer

The general causes for this are as follows:

DISPLAY not set in the environment.
Solution:
```
export DISPLAY=:0.0
./myQtCmdHere
```
( This one doesn't appear to be the one at fault though, as its saying which X display its trying to connect to. Also, its not always 0.0, but most of the time it is )
Non-Authorised User trying to run the X Application
Solution ( as X owning user, ie: yourself )
```
xhost +local:root   # where root is the local user you want to grant access to. 
```