In the samples directory of the Serial Port ActiveX Control you can find "Serial Port Control Center" application, which purpose is to show functionality of the serial port activex control.
Note, that Serial Port Control Center may differ in different programming language version. Samples directory contains the following examples:
Port name: using this list you can choose which port you would like to open
Databits: here you can set the number of its used in byte
Stopbits: specify the number of stopbits here
Parity: configure the parity control settings here
Baudrate: specify the speed for communication with the port here
Log: you can view all the events the opened port will generate
Terminal: you will see all symbols and characters read from or written to the port
To open a port, please, click "Open" button. It will change its caption to "Close" then. It means that the port is opened successfully. Click "Close" to close the port.