[sip-comm] sip communicator+server behind nat


I can't get sip communicator to work with stun01.sipphone.com and
sip.iptel.org because I am behind NAT and can't get udp throughs. Without
setting up a sip gateway, is there any documentation out there on how to set
up the sip-communicator and the jain-sip-presence-proxy. I am a bit lost in
the config files, yet would like to play with this stuff.