How to launch it witho gui?

[lukeprotag]

I am trying to launch this pedsim_ros without gui. But I get :
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.
I even cannot use vncserver, So How can I launch it without gui?