cannot bind to lpd port 631

I removed cups and installed lpdfilter and lprng to use lpd.

When I start lpd I get following error "cannot bind to lpd port 631"

I changed following in /etc/lpd.conf

Lpd_port=632

But I still get the error "cannot bind to lpd port 631"

How can I change the ipp port for lpd so I can use iprint and lpd on the
same server.