flex p2p subscriber cannot receive any video stream (using FMS 4.5)

Hi~

I had wrote a p2p system,

which use adobe FMS 4.5 to be the communication server,

and write the AS3 program for publisher(mobile phone) & subscriber(PC).

this architecture works fine in LAN,

but after deploying FMS to the public IP server,

subscriber will not receive any video stream.

any body knows the problem why?

thanks~