Port numbers are assigned by IANA, you cannot just grab a "free" one.
Look at the IANA register at:
> -----Original Message-----
> From: jehad [mailto:firstname.lastname@example.org]
> Sent: Saturday, August 28, 1999 2:59 PM
> To: email@example.com
> Subject: IPP> proxy & port
> I need your help to find a free proxy address and port.