Check if port is available

Is there any way to check if a port is available at the installation time ?

One of possible ways http://forums.winamp.com/search.php?...der=descending
If you can offer some other way - forum search can help.

i know how i can check if a port is free in windows enviorment
i just wondered if there is any way to do it throgh NSIS
that is i know how to run netstat
but i dont know how to use it correctly in NSIS