You need to configure the necessary port forwarding so that your applications can connect to each other using public IP addresses. If you search google for this topic there are loads of examples:
http://www.wikihow.com/Set-Up-Port-Forwarding-on-a-Router
http://www.howtogeek.com/66214/how-to-forward-ports-on-your-router/
http://portforward.com/
Regards,
Marc