Establishing a NetMeeting Connection with a Firewall
When you use NetMeeting to call other users over the Internet, several IP ports are required to establish the outbound connection. The following table shows the ports, their functions, and the resulting connection.
Port Function Outbound Connection
389 Internet Locator Service (ILS) TCP
522 User Location Service TCP
1503 T.120 TCP
1720 H.323 call setup TCP
1731 Audio call control TCP
Dynamic H.323 call control TCP
Dynamic H.323 streaming Real-Time Transfer Protocol (RTP) over UDP
If you use a firewall to connect to the Internet, it must be configured so that the IP ports are not blocked.
To establish outbound NetMeeting connections through a firewall, the firewall must be configured to do the following:
* Pass through primary TCP connections on ports 389, 522, 1503, 1720, and 1731.
* Pass through secondary TCP and UDP connections on dynamically assigned ports (1024-65535).
The H.323 call setup protocol dynamically negotiates a TCP port for use by the H.323 call control protocol. Also, both the audio call control protocol and the H.323 call setup protocol dynamically negotiate UDP ports for use by the H.323 streaming protocol, called the Real-Time Transfer Protocol (RTP). In NetMeeting, two UDP ports are determined on each side of the firewall for audio and video streaming, for a total of four ports for inbound and outbound audio and video. These dynamically negotiated ports are selected arbitrarily from all ports that can be assigned dynamically.
NetMeeting directory services require port 389. Microsoft Internet Locator Service (ILS) servers, which support the Lightweight Directory Access Protocol (LDAP) for NetMeeting, also require port 389.
Source:
Microsoft