I found the following source. The most important thing for me is:
- an iPhone can send UDP packets to hosts off the AT&T network
- an iPhone can't receive UDP packets sent to it from a host off the AT&T NAT network
- an iPhone SHOULD be able to send & receive UDP packets to other iPhones on the AT&T network.
- We should be able to send DIS from an iPhone to a server
- We should be able to do multicast on a WiFi interface, and send & receive to other
hosts on the same WiFi network
This should also apply to all other smartphones. If you can not receive UDP packages from your phone the packets could be blocked by your Network Provider, or something in your setup is wrong.
The bigger problems seems to me that you are unable to send data back to your phone. That makes all UDP calls a one way route and maybe render your server useless.