As I understood,
In order to initialize P2P connectivity via hole-punching, a device should reside in a non-symmetric NAT (which basically also implies single WAN\External IP Address for outgoing traffic).
I can not find an android app (kind of a little tester app, to open when I'm inside a LAN) that tells what are all or some of my WAN\External IP Addresses.
All apps on Play that I found show me only one External IP Address, even though I test it from Symmetric NATs with multiple WAN\External Addresses.
An easy and quick suggestion would be nice (surfing to multiple "whatismyip" sites each time I want to test it is not easy nor elegant\quick).