Unable to get webcam & Sound in the network

I have 5 computers connected inthe network by proxy. I get all
functions inthe server computer of the 5 computers. But in all other 4
computers I do not get webcam and sound in Yahoo messsenger and some
other programmes also. It generally gives the message that you are
behind the firewall. I updated the firewall but without any result.

Please advise how I can obtain the all functions like the server of my
5 computers.

Thanking you all and Happy New Year 2004.