H.323 uses the following ports, as specified in Appendix D of the H.225.0:
|H.225.0 (secure call signaling for hosts)||1300||TCP||(specified in H.235)|
|Unicast Discovery for Gatekeepers||1718||UDP|
|Registration/Status for Gatekeepers||1719||UDP|
|H.225.0 (call signaling for hosts)||1720||TCP|
|H.225.0 (call signaling for hosts)||1720||UDP||(when using H.323 Annex E)|
Multicast discovery (UDP) for gatekeepers and location requests (LRQs) use multicast address 220.127.116.11 (gatekeeper.mcast.net).
|Microsoft||NetMeeting||yes||yes||?||Toby Nixon: "Microsoft NetMeeting version 2.0 and below uses an
alternative call setup procedure that is permitted for combined
H.323/T.120 terminals. Because NetMeeting was originally a T.120-based
product (without H.323 support), it sets up the T.120 (data conference)
call first, and then the H.323 call. That's why you see the call be
accepted before the Setup is sent; the T.120 call is being connected and
then the audio and video is established using H.323.
In order to take advantage of gatekeeper procedures and for other reasons, however, future versions of NetMeeting will set up the H.323 call first and then add on the logical channel for T.120."