Aqui puedes leer, entre otras cosas:
NetMeeting uses the following Internet Protocol (IP) ports:
Port Purpose
-------------------------------------
Dynamic H.323 call control (TCP)
Dynamic H.323 streaming [Realtime Transport Protocol (RTP) over User Datagram Protocol (UDP)]
To establish outbound NetMeeting connections through a firewall, the firewall must be configured to do the following:
Pass through primary TCP connections on ports 522, 389, 1503, 1720 and 1731.
Pass through secondary UDP connections on dynamically assigned ports (1024-65535).
Si tu lo has hecho funcionar sin habrir puertos, eres un fenomeno
Sigo...
NOTE: Some firewalls are capable of passing through TCP connections on specific ports, but are not capable of passing through secondary UDP connections on dynamically assigned ports. When you establish NetMeeting connections through these firewalls, you are unable to use the audio features of NetMeeting.
Lo dicho, nuetro amado 3com no es capaz abrir puertos dinamicamente, a no ser que tengamos ya ampeado todo el rango, teniendo en cuenta que solo se peuden abrir 64 puertos, y el rango que indica es de mas de 64.000, me explicas como lo has hecho?
sigo...
The H.323 call setup protocol (over port 1720) dynamically negotiates a TCP port for use by the H.323 call control protocol. Also, both the audio call control protocol (over port 1731) and the H.323 call setup protocol (over port 1720) dynamically negotiate User Datagram Protocol (UDP) ports for use by the H.323 streaming protocol, called the real time protocol (RTP). In NetMeeting, two ports are determined on each side of the firewall for audio and video streaming. These dynamically negotiated ports are selected arbitrarily from all ports that can be assigned dynamically.
Creo que esta bastante claro, se negocian dinamicamente.
Como la esperanza es lo ultimo que se pierde, a ver si podemos quedar algun dia en algun directorio y hablamos, y a base de "netstats" vemos que puertos estas usando.
Un saludo.