I have switched off IPV6 on my workstation (and local network). I ran
into a problem with cups.
I could issue a test page with localhost:631. However I could _not_
print from localhost......
The error_log showed:
Unable to bind socket for address [v1.::1]:631 - Cannot assign
requested address.
To solve it I had to put 127.0.0.1:631 in cupsd.conf instead of localhost:631.