most likely your phone's access point doesn't do NAT hair-pin, where a device inside the NAT (your computer) sending a packet to your phone's public IP address isn't routed inside the phone correctly.
if you are doing groups communication (multicast NetStream or NetGroup), you can use IP multicast peer discovery (GroupSpecifier.ipMulticastMemberUpdatesEnabled=true and add an IP multicast address) to work around this issue. otherwise, 1:1 direct connections may not be possible in your configuration.
var groupSpec:GroupSpecifier = new GroupSpecifier(any name);
groupSpec.postingEnabled = true;
groupSpec.routingEnabled = true;
groupSpec.ipMulticastMemberUpdatesEnabled = true;
var groupSpecString:String = groupSpec.groupspecWithAuthorizations();
And this do not work!
Generally p2p works over tethering?