SetCommMask function (winbase.h)

Article
10/13/2021

Specifies a set of events to be monitored for a communications device.

Syntax

BOOL SetCommMask(
  [in] HANDLE hFile,
  [in] DWORD  dwEvtMask
);

Parameters

[in] hFile

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

[in] dwEvtMask

The events to be enabled. A value of zero disables all events. This parameter can be one or more of the following values.

Value	Meaning
EV_BREAK 0x0040	A break was detected on input.
EV_CTS 0x0008	The CTS (clear-to-send) signal changed state.
EV_DSR 0x0010	The DSR (data-set-ready) signal changed state.
EV_ERR 0x0080	A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.
EV_RING 0x0100	A ring indicator was detected.
EV_RLSD 0x0020	The RLSD (receive-line-signal-detect) signal changed state.
EV_RXCHAR 0x0001	A character was received and placed in the input buffer.
EV_RXFLAG 0x0002	The event character was received and placed in the input buffer. The event character is specified in the device's DCB structure, which is applied to a serial port by using the SetCommState function.
EV_TXEMPTY 0x0004	The last character in the output buffer was sent.

Return value

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 SetCommMask function specifies the set of events that can be monitored for a particular communications resource. A handle to the communications resource can be specified in a call to the WaitCommEvent function, which waits for one of the events to occur. To get the current event mask of a communications resource, use the GetCommMask function.

Examples

For an example, see Monitoring Communications Events.

Requirements

Requirement	Value
Minimum supported client	Windows XP [desktop apps \| UWP apps]
Minimum supported server	Windows Server 2003 [desktop apps \| UWP apps]
Target Platform	Windows
Header	winbase.h (include Windows.h)
Library	Kernel32.lib
DLL	Kernel32.dll

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