When the client application makes a request to a port other than the origin port, the server usually returns in its header which origins are allowed, so the browser issues the Warning in its console:
How to solve the problem?
Considering that the server uses PHP, to solve the problem add the following line at the beginning of your code:
<?php
header('Access-Control-Allow-Origin: *');
?>
This will allow requests to be sent from any source.