Changing port number

The default webserver port is 80 so what code change is necessary to use a different port.

Changing the port number in the server code segment below makes the IP address unavailable

// Set web server port number to 80
WiFiServer server(80);

Can anyone advise how the port number can be changed.

Thanks

Since posting the above I have looked further on Github and it seems this is not a simple matter, but would appreciate knowing if anyone has attempted this.