WCF/WF - why we use port number in d webservice url

why we use port number in d webservice url should that port number match with the specified port number in web service web config.  The webservice will be called as wcf webservice using that port number....?

Some companies will block various well known ports and insist that incoming public traffic to their web services be done through specific ports.  Sometimes, they'll even assign different ports to different clients.  It can make it easier to react to denial of service attacks in some situations.

Thank you perfectly explained