In this post I am going to demonstrate that how remotely control LED and how it can be connected to Raspberry Pi using MQTT protocol and control GPIO pins using pi4j library. This work is done using Java code. Recently I bought Raspberry Pi 2, so I just wanted to do some learning stuff, basically how to blink (on/off) LED remotely. I have performed extensive survey about Raspberry Pi on internet I found lots of stuff about connect LED with Raspberry Pi via GPIO pins. This created a lots of interest. So I m searched Java library to control gpio pins and I got pi4j library . Actually pi4j library easy to learn and provide bunch of examples. Details of its are mentioned below: