EscapeCommFunction function (winbase.h)

Directs the specified communications device to perform an extended function.

Syntax

BOOL EscapeCommFunction(
  [in] HANDLE hFile,
  [in] DWORD  dwFunc
);

[in] hFile

A handle to the communications device. The CreateFile function returns this handle.

[in] dwFunc

The extended function to be performed. This parameter can be one of the following values.

Value	Meaning
CLRBREAK 9	Restores character transmission and places the transmission line in a nonbreak state. The CLRBREAK extended function code is identical to the ClearCommBreak function.
CLRDTR 6	Clears the DTR (data-terminal-ready) signal.
CLRRTS 4	Clears the RTS (request-to-send) signal.
SETBREAK 8	Suspends character transmission and places the transmission line in a break state until the ClearCommBreak function is called (or EscapeCommFunction is called with the CLRBREAK extended function code). The SETBREAK extended function code is identical to the SetCommBreak function. Note that this extended function does not flush data that has not been transmitted.
SETDTR 5	Sends the DTR (data-terminal-ready) signal.
SETRTS 3	Sends the RTS (request-to-send) signal.
SETXOFF 1	Causes transmission to act as if an XOFF character has been received.
SETXON 2	Causes transmission to act as if an XON character has been received.

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Requirement	Value
Minimum supported client	Windows XP [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps \| UWP apps]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll