Recently I was attempting to setup a VNC connection to a remote server (using the tigervnc-server-minimal RPM on Fedora), but wanted to use XDM for the login information so that I didn't have to create seperate login credentials. Following guides online such as this one: I didn't have too much trouble configuring everything. The problem, however, was that when I attempted to connect to the remote VNC session all I got was just a black screen with a square mouse cursor on it, the XDM login screen never appeared. The solution for this was rather simple, inside of the /etc/xinetd.d/vnc-server script, I replaced the word localhost with the localhost IP instead,

This line gave me a black screen when logging in remotely
server_args = -inetd -query localhost -once -geometry 1670x1030 -depth 16 -securitytypes=none

This line resolved my black screen login issue with VNC
server_args = -inetd -query -once -geometry 1670x1030 -depth 16 -securitytypes=none