firwall detection ?

[Sonu_Kapoor]

hey guys,

I need urgently your help. I need to know whether it is possible to detect if the client is behind a firewall or not. Is there any way to do this ? If not in php maybe in an another scripting language ?

Thanks guys, Sonu

[LordShryku]

I guess you could using [man]fsockopen[/man] on a port of your choosing.

[Sonu_Kapoor]

And which port should be checked ?

Thanks

[LordShryku]

Probably some high up, never used port. Something that a common firewall would black. Why would need this information anyway?