[Asterisk-Users] Registering Remote Sipura to Asterisk (both behind firewall)

[Joseph]

Can anybody point or provide working configuration how to register
Sipura to Asterisk over the Internet. Both Sipura and Asterisk are
behind firewalls. 

I'll be force to use SIP as that is the only protocol that Sipura is
using. 
Do I need to enter any "STUN Server:" setting in "SIP" tab. 

On Asterisk I think I only need to make changes in sip.conf isn't it? 
What ports do I need to open on my firewall?

-- 
#Joseph