[Zope] multiple zope instances on one ip address

[matt]

I am trying to set up more than one zope instance and failing...

I have configured two seperate installations (different versions, in fact)
of zope, and lets say I try to run one on 192.168.0.1:2000 and the other
on 192.168.0.1:8000.  If the port 2000 one starts first, it will also
answer requests for port 8000.  If I then kill the port 2000 one, the port
8000 one will then be able to answer requests.  I want both to run without
interfering with each other.

BTW, I start them with:
firstinstance/z2.py -X -w192.168.0.1:2000 -u nobody
secondinstance/z2.py -X -w192.168.0.1:8000 -u nobody

If this just the way things are, or am I missing something?

thanks!