How to check for free ports on Linux Box

["Kaushal Shriyan" <kaushalshriyan gmail com>]

Hi

I need my apache web server to listen to a particular port, On my box
there are 100 of applications which uses port to run

My Query is how do i check for FREE PORTS on my box, is there any
utility where i can find FREE Ports and use it for my application(Apache Web
Server)

Thanks and Regards

Kaushal