Before USB ports became standard on PCs, several devices connected through a serial port. They're obsolete in many ways, but ...

A name assigned to a hardware device that represents its physical address. For example, COM1 stands for serial port #1 in a PC. See COM1. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other ...

Each device is both a transmitter and ... But some programs, like cutecom, for example, know too much about what a serial port is supposed to look like so you can’t open a pty with them.

The back device is, usually, your normal serial port. The frontend device is something ... but it is easy to parse by other programs including an example Perl program included with it.