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).
I've written an Android App that make multiple requests to multiple servers,
and prints the External IPs it used in the requests.
I tested it from several Symmetric NAT networks and it seems to work properly.
That's what I needed.
If someone is interested, I called it "External IPs Revealer \ Internet Checker":
App on Google Play