Direct cable connection to a standard serial cable) must be used to connect each of the two computers to communicate properly. Such connection uses PPP protocol. If the parallel ports are used, Windows supports standard or basic 4-bit cable (commonly known as LapLink cable), Enhanced Capabilities Port (ECP) cable, or Universal Cable Module (UCM) cable (which was known as DirectParallel cable by Parallel Technologies). Infrared communication ports, like the ones found on laptop computers (such as IrDA), can also be used. Connecting any two computers using USB requires a special proprietary bridge cable. A directly connected pin-to-pin USB type A cable does not
Parallel port later than Windows 95/98 prevent user programs from directly writing to or reading from the LPT without additional software (kernel extensions). Current CNC Milling Machines also often make use of the parallel port to directly control the machine's motors and attachments. Traditionally IBM PC systems have allocated their first three parallel ports according to the configuration in the table below (if all three printer ports exist). If there is an unused slot, the port addresses of the others are moved up. (For example, if a port at 0x3BC does not exist, the port at 0x378 will then become the first