Tcp Com Bridge allows you to create a virtual COM port with any number. When choosing a number for the virtual port, you should not select any port numbers that already exist on your computer. You can check which ports are in use via the Device Manager. Please note that Device Manager displays not all existing COM ports. To check if a port already exists, try creating a configuration without creating a virtual COM port. If there is no such port on your computer, Tcp Com Bridge will display a message informing you about that. As a rule, port numbers starting from 10 are not used.