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WaitCommEvent (Windows CE 5.0)

Windows CE 5.0
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This function waits for an event to occur for a specified communications device.

The set of events monitored by WaitCommEvent is contained in the event mask associated with the device handle.

BOOL WaitCommEvent(
  HANDLE hFile, 
  LPDWORD lpEvtMask, 
  LPOVERLAPPED lpOverlapped


[in] Handle to the communications device.

The CreateFile function returns this handle.

[out] Long pointer to a 32-bit variable that receives a mask indicating the events that occurred.

If an error occurs, the value is zero; otherwise, it is one or more of the following values.

EV_BREAKA break was detected on input.
EV_CTSThe CTS (clear-to-send) signal changed state.
EV_DSRThe DSR (data-set-ready) signal changed state.
EV_ERRA line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY.
EV_POWERPower event, which is generated whenever the device is powered on.

This value is specific to Windows CE.

EV_RINGA ring indicator was detected.
EV_RLSDThe RLSD (receive-line-signal-detect) signal changed state.
EV_RXCHARA character was received and placed in the input buffer.
EV_RXFLAGThe 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_TXEMPTYThe last character in the output buffer was sent.
[in] Ignored; set to NULL.

Return Values

Nonzero indicates success.

Zero indicates failure.

To obtain extended error information, call the GetLastError function.


The WaitCommEvent function monitors a set of events for a specified communications resource. To set and query the current event mask of a communications resource, use the SetCommMask and GetCommMask functions. When a communications event that is set by SetCommMask occurs, WaitCommEvent returns.

Only one WaitCommEvent can be used for each open COM port handle. This means that if you have three threads in your application and each thread needs to wait on a specific comm event, each thread needs to open the COM port and then use the assigned port handle for their respective WaitCommEvent calls.


OS Versions: Windows CE 1.0 and later.
Header: Winbase.h.
Link Library: Serdev.lib.

See Also

CreateFile | GetCommMask | SetCommMask | SetCommState | DCB

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