Re: Firewall : ports for TCP and UDP Connections

Daniel Chung-Chi Chuang (
Wed, 26 Mar 1997 09:56:53 +0000

Bill Woodland (Squeek) wrote:
> As far as I know, the only TCP that the CU client does is the
> gethostbyname() function (Steve Edgar or Brian O'Shea correct me if I'm
> wrong). The client does everything else via UDP on port 7648.

It is not clear what the tcp session is used for. The gethostbyname()
will get ip address from the domain name provided. How will this
function get used ? The client always uses the same port 7649. I
suspect the client call bind() with port 7649. It means every time
the tcp connection is closed, TIME_WAIT state will keep you from
starting the cu-seeme application at least 2MSL period.

> Open up UDP ports 7640 thru 7648

It is unsafe to open all UDP ports from 7640 to 7648 until you know
the application is secure enough. How can we know the cu-seeme
application is secure without any technical information ? Another
way to learn it is by reading the source code directly. Are there
any open domain ( free ? ) source code available now ? By the way,
What about the port 7649 used for WhitePine ?

Best Regards,
Daniel Chuang