Virtual Serial Port ActiveX Control provides a set of events to control virtual serial port state changes:

EventBrief Description
OnBaudRateBaud rate change was detected
OnDTRDTR (data-terminal-ready) signal state changed
OnHandFlowFlow control change detected
OnLineControlLine control change detected
OnOpenClosePort Open or Close operation detected
OnRxCharA character was received and placed in the input buffer
OnRTSRTS (ready-to-send) signal state changed
OnSpecialCharsChange of event (special) characters was detected
OnTimeoutsTimeouts change was detected
OnEventTriggered every time a communication event occurs
OnBreakBreak signal state changed