Car to Arduino Communication: CAN Bus Sniffing and Broadcasting With Arduino

From Wikipedia, the Controller Area Network (CAN) bus is a "vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer." These devices can also be referred to as electronic control units (ECUs). Essentially the CAN bus is a bunch of linked ECUs within the vehicle that communicate with each based on a broadcast. Every ECU intercepts every broadcast, but individually decide whether or not to react to it.