PurgeComm

The PurgeComm 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,  // handle to communications resource
  DWORD dwFlags  // action to perform
);
 

Parameters

hFile

Handle to the communications resource. The CreateFile function returns this handle.

dwFlags

Specifies the action to take. This parameter can be a combination of the following values:

Value	Meaning
PURGE_TXABORT	Terminates all outstanding overlapped write operations and returns immediately, even if the write operations have not been completed.
PURGE_RXABORT	Terminates all outstanding overlapped read operations and returns immediately, even if the read operations have not been completed.
PURGE_TXCLEAR	Clears the output buffer (if the device driver has one).
PURGE_RXCLEAR	Clears the input buffer (if the device driver has one).

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.

Remarks

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). Note, however, that FlushFileBuffers is subject to flow control but not to write time-outs, and it will not return until all pending write operations have been transmitted.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.

See Also

Communications Overview, Communication Functions, CreateFile