Failed to connect Mobile First server using angular

Question

When ever i am trying to connect from device, always i am getting the below error

The connection to the server was unsuccessful

fille:///android_asset/www/index.html

In appcomponent added the below code.

   WLAuthorizationManager.obtainAccessToken()
        .then(function (accessToken) {
        alert("Connected to MobileFirst Server");
    }, function (error) {
        alert("Failed to connect to MobileFirst Server");
    });

I am using angular cordova.