Serial to WiFi converters can wirelessly enable dumb RS232, RS422 or RS485 devices. They can be used in two different fundamental modes of operation:
Ad-hoc mode: A pair of serial to WiFi converters are configured to directly address each other: What goes in one end comes out of the other much like a pair of radio modems.
Infrastructure mode: One or many serial to WiFi converters behave as wireless clients associating with a WiFi Access Point (AP). This means the serial data is passed to the AP then on to a wired network where it can be configured to appear as a virtual COM port in a PC or transmitted back out of a wired serial to Ethernet converter.