I am trying to run a program (A tcpdump like GUI) that needs to be run as root in order to put the interface into promisc mode. When I open up a shell and run the program, I get :

Xlib: connection to ":0:0" refused by server
Xlib: Client is not authorized to connect to Server

Gtk-WARNING **: cannot open display 0:0

I can run the prog as a normal user, but cannot put the interface in promisc mode. I can run the prog as root fine, if I log into KDE as root. So my question, how do I run it after having su'ed to root within a shell? The program will not run suid.