Sipdroid works on symmetric NAT! Help on desktop ? (off-topic)

[Rescondio]

Hello,

I'm surprised to see that sipdroid works perfect on my LAN, behind a
symmetric NAT that I am no able to configure.

I've tried to use PBXES from inside this network for some time from my
Ubuntu laptop with no luck. I've tried Twinkle, ekiga and some others
SIP clients, but I was not able to connect to PBXes.

Please, any of you knows if there is some desktop software that uses
the same techniques as Sipdroid for connecting to PBXES so I can
finally use it from my desktops ans laptops ?

If not, there is any way to use sipdroid on Linux ?

Thank you so much in advance !!!