Anwendungs Server als Client betreiben mit Indy

[QuickAndDirty]

I want to sent large amounts of data over this Server.
So would STUN work?
I mean it would be pretty good if I could actually use the STUN from google.

It's immportant to know that the Windows-Server-Service will be behind different corporate firewalls I can't control (And apparantly even most admins suck at adminstrating those systems).
The Mobile Apps know the WAN-IP of the Windows-Server.
But there are many Mobile Apps and many different organizations with their own Windows-Server.
And the data should allways be sent over the STUN Server . No real peer2peer conection. no interactive exchange of adresses.