SSLTest project Unable to bind to port

Please excuse my newbie question on the Xojo SSLTest project for Xojo Web.
When I do a run paused, it fires up, but with the Unable to bind error when I start the App from the command line;

MacBook-Pro-Boudewijn:SSLTest.debug bkrijger$ ./SSLTest.debug --secureport=9090
Application is ready
App is shutting down: Unable to bind to port 9090, port is already in use.
Transactions: 0
Traffic Received: 0 b
Traffic Served: 0 b
Total Traffic: 0 b
Average Traffic Per Transaction: 0 b

Can anyone tell me why I’m getting the Unable to Bind error and how to fix this?

Thanks in advance.

That means that the port is in use. Look at your activity viewer and see if a copy of your app is already running.

Also, do you have an SSL certificate in the folder where the app is launching from?