[nsd-users] nsd can't bind udp socket: Address already in use

[Jaap Akkerhuis]

    If you want to use nsd to host some domains, and use unbound for
    resolving the normal way with a special forward to those nsd domains,
    you should run nsd on another port like 5353 and configure unbound
    forward zones to point to 127.0.0.1 at 5353 for those zones.

As Anand has already has pointed out on the Mac port 5353 is likely to be
used buy mdns. Nowadays, it is even documented as a port reserved for this
purpose:

grep 5353 /etc/services
mdns            5353/tcp   #Multicast DNS
mdns            5353/udp   #Multicast DNS

(This is on a FreeBSD machine)

The same file suggests:
# The Dynamic and/or Private Ports are those from 49152 through 65535
so pick one in that range to be on the safe side.

	jaap