XData + CORS


I have a problem with XData server and web client.
The XData server is running on port 4711, the web server is running on the same server on port 80.
CORS is on, port 4711 is blocked in the firewall, so not everyone can access the REST data.
If I test the web client with the browser of the server, then everything works, if I call the website from another browser, then comes the error message that the database can not be opened.
Where is my mistake?

thanks for answer