Ionic 2 No 'Access-Control-Allow-Origin' header is present

[rabernet]

Why i test my app in heroku node.js socket.io basic conection.

But in angular 1, angular 2, Ionic 2.

Appear:
XMLHttpRequest cannot load https://xxxxxx.herokuapp.com//socket.io/?EIO=3&transport=polling&t=LinPHk2. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:XXXX' is therefore not allowed access.
No 'Access-Control-Allow-Origin' header is present

Thanks.