How to solve CORS policy problem for Strapi?

That is a good observation. I don’t know how to see the requesting from the device. The code works perfectly from my localhost requesting to my virtual server. Once, on a minor version (<3.0.0) of strapi I could configurate the server and the client, using config/enviroment/… folders and JSON config archives. But, this is not working anymore. I upgrade strapi and configurated middleware.js, but it is not work.
I checked my connection from my device to the server via ping. But, when I tried to access to the server using postboy from the mobile, I obtained an error.

private server = 'http://192.168.0.50'; private port = '1337';

getLoginStr(){
     return this.server + ':' + this.port + '/auth/local';
 }

That way, I construct my address for login to strapi.
I know there is an issue connecting from webview that makes different the origin and strapi looks that like a different source. But, I couldn’t find the solution…