Allowing programs run by regular users to open ports below 1024
Normally, only the root user is allowed to open ports below 1024.
That’s why, if you try running an application as a normal (non-root) user, and that application tries to open a port below 1024, you’ll get an error (access denied most likely).
If you’re running Fedora (and that would probably work on other distros too), there’s a command you can run, as root, that will allow such programs to open any of those ports, even if they’re run by a regular user.
setcap cap_net_bind_service=ep your-program-name
setcap cap_net_bind_service=ep /usr/local/bin/znc
You’ll then need to restart the program, if it was already running.