Looking at netstat, a running pdns_server has a couple of extra ports open besides the standard udp/53 and tcp/53.
With webserver=no, there's a 127.0.0.1:8081 port open. Setting webserver-port= to empty does not solve the problem, there's still a random port open after every restart.
Also there are two other random ports open listening on udp/0.0.0.0 and udp6/:: . There is no recursor set up in pdns.conf (recursor=no, allow-recursion=no)
# netstat -nlp |grep pdns_server |grep -v ":53"
tcp 0 0 127.0.0.1:33188 0.0.0.0:* LISTEN 3695/pdns_server-in
udp 0 0 0.0.0.0:44410 0.0.0.0:* 3695/pdns_server-in
udp6 0 0 :::33604 :::* 3695/pdns_server-in
Forgot to mention:
Nov 17 11:48:08 ds9 pdns: PowerDNS 3.0 (C) 2001-2011 PowerDNS.COM BV (Jul 22 2011, 11:09:26, gcc 4.4.5) starting up
the port being open, I can't reproduce that in 3.1. The other ports are required for notifications and powerdns internal queries.
(The fix was in r2269)