LapLink cable
A Laplink® Cable, also known as null-printer cable, allows the connection of two computers via the parallel port to establish a direct cable connection.
The cable was introduced in 1983 with the "LapLink" software package, from Traveling Software, to allow fast data transfer between the early PCs running MS-DOS, giving much faster transfer rates than the traditional null modem serial cable. At the time, almost all PCs had a parallel printer port, but neither USB nor modern Ethernet was available.