A device that already includes a standard serial port, for example, can connect to a LAN or WLAN so it can communicate with other devices and let people remotely control it, make measurements, and ...

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

An image from H.D. Moore's presentation on serial server security vulnerabilities, showing an oil and gas infrastructure setup networked with serial port connections. (Click to enlarge.) You ...