GetCommModemStatus

The GetCommModemStatus function retrieves modem control-register values.

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

Parameters

hFile

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

lpModemStat

[out] Pointer to a variable that specifies the current state of the modem control-register values. This parameter can be one or more 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.

Requirements

  Windows NT/2000: Requires Windows NT 3.1 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Declared in Winbase.h; include Windows.h.
  Library: Use Kernel32.lib.

See Also

Communications Overview, Communication Functions, CreateFile, WaitCommEvent