Add firewall rule programmatically

Question

I am developing an application for Mac, and wants to add firewall rule when my application launches,

would like to know the entry point, if anyone has any idea,
I guess, i need to modify
/Library/Preferences/com.apple.sharing.firewall.plist
But this file is not present in my Machine and any info about structure of this file ?

Requirement is something like this

When it runs, then browser shouldn't allow to open some particulars website, so i believe, this is going to be a application level firewall.

Answer 1

Thanks for looking at it, Finally i am using ipfw to do so, but still not yet clear about how to configure the rule