EV_BREAK   A break was detected on input. 
EV_CTS     The CTS (clear-to-send) signal changed state. 
EV_DSR     The DSR (data-set-ready) signal changed state. 
EV_ERR     A line-status error occurred. Line-status errors are        CE_FRAME, CE_OVERRUN, and CE_RXPARITY. 
EV_RING    A ring indicator was detected. 
EV_RLSD    The RLSD (receive-line-signal-detect) signal changed state. 
EV_RXCHAR  A character was received and placed in the input buffer. 
EV_RXFLAG  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 The last character in the output buffer was sent.