Webware is listening on 0.0.0.0 which means all configured IPv4 interfaces. That would include the loopback 127.0.0.1 address assigned to the lo interface:
root@mrpc:~# netstat -ntlp|grep 9000
tcp 0 0 0.0.0.0:9000 0.0.0.0:* LISTEN 4251/python
root@mrpc:~# ifconfig lo
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
root@mrpc:~# cat /etc/hosts
127.0.0.1 mrpc.peterlyons.com mrpc localhost.localdomain localhost plwiki.peterlyons.com plwiki stage.peterlyons.com stage
# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
I think you are probably correct that there is some IPv4/IPv6 issue at play here, but I don't know what that would be exactly.
Is Webware listening on 127.0.0.1 or localhost? I think there can be a TCP IP v4/v6 problem.