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Q: MS NetMeeting: establishing connection but no voice/data being transmitted ( Answered,   1 Comment )
Subject: MS NetMeeting: establishing connection but no voice/data being transmitted
Category: Miscellaneous
Asked by: ez13-ga
List Price: $5.00
Posted: 24 Dec 2002 21:20 PST
Expires: 23 Jan 2003 21:20 PST
Question ID: 133250
Technical problem using MS NetMeeting: when attempting to connect for
video-conferencing with another IP-client, we manage to establish a
secure connection (as per the status shown at the bottom of the
netmeeting window), but neither  video nor voice is transmitted via a
live, open connection.
attempting to IM chat via netmeeting works, indicating that the
point-to-point connection is established but, again, neither voice nor
data is transmitted via continous, open connection. one thing i noted
is that under Tools_Video menu,
the 'Send' command is active and checked; the 'Receive' command is
inactive (appearing in grey with no chance to check or uncheck).

How do I trouble-shoot this problem, allowing for full voice and data
transmission via the netmeeting application?

Things to note:
1. the setup has worked previously
2. only change to the setup is that i am now using a wireless router
(perhaps the security settings on the router allow for a connection to
be established but block the trasmittal of the data?)
3. the camera is working (i can see my own image on the screen)
4. every indication shows that the point-to-point connection is being
established (as mentioned above)

Request for Question Clarification by snapanswer-ga on 25 Dec 2002 14:26 PST
What were you using to connect to the Internet before?  Was it an
ethernet cable connection to a hub or router or was it a dial-up

Are you familiar with your wireless routers "firewall" settings and
enabling ports?

Have you installed a software firewall?
Subject: Re: MS NetMeeting: establishing connection but no voice/data being transmitted
Answered By: jeremymiles-ga on 25 Dec 2002 15:08 PST
You need to set up port forwarding on the router, to tell the router
to send information to your PC. Most routers act as a hardware
firewall, so you need to look at the instructions to see how port
forwarding works on the router.

The following information is taken from:

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

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.

[end quote]

I have found that because Netmeeting uses dynamic allocation, you need
to open a lot of ports to make it work.

I hope that this has answered your question - if not please request
clarification, and I will try to help you out.  It can be a bit
fiddly, especially the first time that you try it.

Search strategy:
netmeeting ports

(The use of only searches microsoft's site.)

Subject: Re: MS NetMeeting: establishing connection but no voice/data being transmitted
From: stunted-ga on 09 Jun 2004 20:30 PDT
In general all H.323 software (including NetMeeting) is highly
allergic to any kind of NAT firewall, some manufacturers of such
devices do build in H.323 support, for instance the Linksys BEFSR41
router supports outgoing H.323 calls, and version 2 of that router
supported incoming calls just by forwarding ports 1720 and 1503 to
your PC, however Linksys stopped this support with version 3 of the
router. I have found the easiest solution is to dig out an old PC and
install Smoothwall ( and use that as a your
firewall, to enable incoming calls just forward ports 1720 and 1503 to
your PC. If you prefer a hardware solution, look here

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