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EscapeCommFunction info  Overview  Group

The EscapeCommFunction function directs a specified communications device to perform an extended function.

BOOL EscapeCommFunction(

    HANDLE hFile,

// handle to communications device

    DWORD dwFunc 

// extended function to perform



Identifies the communications device. The CreateFile function returns this handle.
Specifies the code of the extended function to perform. This parameter can be one of the following values:




Clears the DTR (data-terminal-ready) signal.


Clears the RTS (request-to-send) signal.


Sends the DTR (data-terminal-ready) signal.


Sends the RTS (request-to-send) signal.


Causes transmission to act as if an XOFF character has been received.


Causes transmission to act as if an XON character has been received.


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.


Restores character transmission and places the transmission line in a nonbreak state. The CLRBREAK extended function code is identical to the ClearCommBreak function.

Return Values

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.

See Also

ClearCommBreak, CreateFile, SetCommBreak 

See also:

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