The built-in, nine-pin serial port on an H/PC operates identically to the RS232-compliant serial port on a desktop computer. Windows CE provides support for applications that communicate over the built-in serial port by exposing many of the serial functions, file functions, and Windows Socket functions that are used by Windows communications applications.
Unlike Windows desktop platforms, the Windows CE CreateFile function requires a colon appended to the device name. In most cases, "COM1:" designates the built-in serial port on an H/PC.