This is a example to implement a web app with Node.js running on Raspberry Pi, to receive command from client, and control connected Arduino Esplora's LED. All clients share a common hardware: when a client toggle the LED, all clients will be updated accordingly.
Hello Raspberry Pi:
http://helloraspberrypi.blogspot.com/...
Arduino-er
http://arduino-er.blogspot.com/2014/0...