Does T-Mobile network allow incoming UDP packets?

Question

Short version: Does the T-Mobile network allow incoming UDP packets?

Longer version:

I'm writing a small test app that connects two Androids over a mobile network. It works over LAN but not over 3g.

Most carriers block incoming TCP connections over their networks, Does the same restriction apply to incoming UDP?

Answer 1

I've recently been testing UDP port forwarding on 3G from T-Mobile Slovakia (Deutsche Telekom) and found that it's not possible. They are using Symmetric NAT which will prevent you from communicating endpoints between two peers because one peer's incoming port will depend on another peer's IP address. I wrote a bit more about it here.

I've not yet had problems with O2 Slovakia (Telefónica) in this regard.

EDIT: This may be irrelevant now given that the question is 5 months old, but since you mentioned building a test app, the best tutorial on NAT traversal I've found is IMO this one.