I have set up tigervnc-server on my CentOS 6 machine following this guide. At first everything worked fine, I could connect to the server using TightVNC Viewer on my Windows machine. I left the session running in the background for a while. The server closed the inactive connection, which it also does for ssh or any other connections, so that's still normal. So I reconnected and everything was fine.
Then I decided to add a different user to the VNC users, as I was running my first connections from root. That's where it all broke. I couldn't connect to he server anymore, it always told me that the remote computer denied the connection. I made sure the server ports were open in iptables, tried to reinstall tigervnc-server, changing the config back to how it was before it broke and disabling the Windows Firewall. After reinstalling it, I was able to launch it without setting a vnc password, so it either saved it somehow from before or something broke entirely. None of my attempted fixes worked.
Turned out to be me not working on linux for over a year and I finally figured out I had to start the vnc server from the user I wanted it to run on.