GetCommModemStatus

The GetCommModemStatus function retrieves modem control-register values.

BOOL GetCommModemStatus(
  HANDLE hFile,        // handle to communications device
  LPDWORD lpModemStat  // pointer to control-register values
);
 

Parameters

hFile

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

lpModemStat

Pointer to a 32-bit variable that specifies the current state of the modem control-register values. This parameter can be a combination of the following values:

Value	Meaning
MS_CTS_ON	The CTS (clear-to-send) signal is on.
MS_DSR_ON	The DSR (data-set-ready) signal is on.
MS_RING_ON	The ring indicator signal is on.
MS_RLSD_ON	The RLSD (receive-line-signal-detect) signal is on.

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

The GetCommModemStatus function is useful when you are using the WaitCommEvent function to monitor the CTS, RLSD, DSR, or ring indicator signals. To detect when these signals change state, use WaitCommEvent and then use GetCommModemStatus to determine the state after a change occurs.

The function fails if the hardware does not support the control-register values.

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, WaitCommEvent