Let me start by saying I've found several proposed solutions online, but none of them seem to work for me.
Issue:
I have a meteor app I'm trying to run on android. For this, I've deployed the app on Heroku and I call the run android-device command using the --mobile-server https://myapp.heroku.com parameter.
I permanently receive the error
"XMLHttpRequest cannot load https://myapp.heroku.com/sockjs/... . No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:12848' is therefore not allowed access. The response had HTTP status code 404.", source: http://localhost:12848/ (0)
Here is what I've tried so far:
I set ROOT URL at meteor startup:
  process.env.ROOT_URL = "https://myapp.heroku.com";  
I tried setting the Access Control like this, server-side at meteor startup:
  WebApp.connectHandlers.use(function(req, res, next) {
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.header('Access-Control-Allow-Methods', 'GET, PUT, POST, DELETE, OPTIONS');
    res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
    res.header('Access-Control-Allow-Origin', 'https://myapp.heroku.com');
    res.header('Access-Control-Allow-Origin', 'http://localhost:12848');
    res.header('Access-Control-Allow-Origin', 'http://meteor.local');
    res.header("Access-Control-Allow-Headers", "Content-type,Accept,X-Custom-Header");
    return next();
  });
I tried to use the browser-policy package, like this, server-side at meteor startup:
  BrowserPolicy.content.allowSameOriginForAll();
  BrowserPolicy.content.allowOriginForAll('*');
  BrowserPolicy.content.allowOriginForAll('http://meteor.local');
  BrowserPolicy.content.allowOriginForAll('https://myapp.heroku.com');
  BrowserPolicy.content.allowOriginForAll('https://*.myapp.heroku.com');
  BrowserPolicy.content.allowEval();
I tried adding access rules to "mobile-config.js":
App.accessRule("*");
I made sure the name in the "package.json" file under root is identical to the App name under "mobile-config.js"
What else am I missing?
Edit:
I've also tried adding the express and cors packages to whitelist local host:
  var whitelist = [
  'http://localhost:3000',
  'http://localhost:12848',
  'https://myapp.heroku.com'
  ];
  var corsOptions = {
      origin: function(origin, callback){
          var originIsWhitelisted = whitelist.indexOf(origin) !== -1;
          callback(null, originIsWhitelisted);
      },
      credentials: true
  };
  app.use(cors(corsOptions));
Also tried to enable pre-flight, like this:
app.options('*', cors())
 
    