Printers connected to a PC do not use a unique port. 631 happens to be the port that the CUPS print server runs on. If you want to connect to a printer on a window PC you will need to configure file and print sharing. Then you will need to configure samba on the linux box. See www.samba.org
BTW for reference smb, netbios i.e. windows file and printer sharing uses ports 137,138 and 139.