This function can discard all characters from the output or input buffer of a specified communications resource.
It can also terminate pending read or write operations on the resource.
BOOL PurgeComm( HANDLE hFile, DWORD dwFlags );
[in] Handle to the communications resource.
The CreateFile function returns this handle.
[in] Specifies the action to take. The following table shows possible values.
Terminates outstanding overlapped read operations and returns immediately, even if the read operations have not been completed.
Clears the input buffer, if the device driver has one.
Terminates outstanding overlapped write operations and returns immediately, even if the write operations have not been completed.
Clears the output buffer, if the device driver has one.
Nonzero indicates success. Zero indicates failure. To obtain extended error information, call the GetLastError function.
If a thread uses PurgeComm to flush an output buffer, the deleted characters are not transmitted.
To empty the output buffer while ensuring that the contents are transmitted, call the FlushFileBuffers function (a synchronous operation).
FlushFileBuffers is subject to flow control but not to write timeouts, and it does not return until all pending write operations have been transmitted.