WhatsApp Clone with Meteor CLI and Ionic: Fail to connect to DB on Android

I have some experience with Meteor but I am now trying to have a Meteor app for Android. To get to known some new logic, I follow the whatsapp tutorial . The most new things go rather well but I do fail to connect the MongoDB or my collections from within the Android App, while I can access the MongoDB from within a browser (both on phone and desktop) so it is clearly a problem related to the mobile app. I host my mongoDB on digitalocean so there cannot be any problems related to localhost or whatever. Is there anyone else who ever had issues with this and is there a solutions for it?

Btw: I finished step 4 of the tutorial…

Thanks in Advance