Explore this tutorial  demonstrating how the Arduino Yún can be controlled from anywhere with any internet connected web browser. The solution is provided by Bo Peterson using the Yaler service which means that the Yún can be reached from any network without knowing the IP-address, and without any port forwarding on the router where the Yún is connected.

A common problem in home automation and internet of things applications is that it is difficult to reach devices connected behind wifi routers from the outside. There are different approaches to overcome this problem:

• Port forwarding and static ip addresses. This solution requires the user of the connected device to know how to configure a router and have access to router administration which is not always possible. A Yun tutorial with port forwarding is found here.
• Polling is a technique where the connected device at regular intervals checks with an external server if the device should take action. This solution requires no configuration of the router but it creates extra network traffic and response delays.
• A third way is to use WebSockets which is a way of providing real time full-duplex communication over TCP. Spacebrew is a good open source toolkit for connected devices using WebSockets. Autobahn is another infrastructure that can be used.
• Reverse HTTP is the solution that will be used in this tutorial. We will use Yaler which is an open source relay infrastructure that gives access to connected devices with very little configuration.

Follow the tutorial and get the code at this link.