Comment 32 for bug 304393

The problem is that other daemon grab this port before cupsd gets a chance, typcally rpc. See:
https://bugzilla.redhat.com/show_bug.cgi?id=103401

Work around:
lsof -i :631
stop or kill the process, restart cups

long term solution:
I guess distros should ensure processes use different port number.

Note:
The same problem happens on a workstation that try to browse for remote printers (cupsctl --remote-printers), you don't get an error, but "lpstat -a" doesn't show remote printers.