CUPS does not receive browsing information

Problem

You are using CUPS (Common Unix Printing System) as local printing spooler. You are using SuSE Linux 9.0 (this problem may occur on other systems as well). You want CUPS to receive broadcast information about printers in the network neighbourhood from other CUPS servers. This does not work. Maybe it does only work sometimes.

In your logfile e.g. /var/log/cups/error_log you see the error message

StartBrowsing: Unable to bind broadcast socket - Address already in use.

Reason

The portnumber CUPS uses to send and receive browsing packets is 631. This is already in use by the rpc.mountd which is started by the NFS server daemon. You can check this using pmap_dump:

# pmap_dump
    100000    2   tcp    111  portmapper
    100000    2   udp    111  portmapper
    100021    1   udp  32768  nlockmgr
    100021    3   udp  32768  nlockmgr
    100021    4   udp  32768  nlockmgr
    100021    1   tcp  32768  nlockmgr
    100021    3   tcp  32768  nlockmgr
    100021    4   tcp  32768  nlockmgr
    100024    1   udp    801  status
    100024    1   tcp    804  status
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100005    1   udp    631  mountd
    100005    1   tcp    635  mountd
    100005    2   udp    631  mountd
    100005    2   tcp    635  mountd
    100005    3   udp    631  mountd
    100005    3   tcp    635  mountd

The portmapper assigns random port numbers. In your case it assigned unfortunately the port number 631.

Resolution

Restart your NFS server daemon (/etc/init.d/nfsserver restart).

If you want to make sure, that this never happens again, you can edit /etc/init.d/nfsserver and call /usr/sbin/rpc.mountd with a fixed portnumber, e.g. 635:

/usr/sbin/rpc.mountd -p 635

Keywords: cups portmap nfsserver port 631 suse   Author: Mathias Kettner