Itunes sharing

I would like to share an itunes library network in Forefront, Forefront Tmg server blocks customer access to it, I tried to open the ports 3689 tcp 5353 udp i but nothing, it seems that the client sends a query to the external 224.0.0.251 but this is not in the configuration or network paths do not see a way, this is a multicast query but not as enabling it to find the shared pc with itunes.

Any tips?