MTP allows the device to initiate events (e.g., ObjectAdded when a photo is taken). A good porting kit includes an event queue so the device can push updates to the host without polling.
Reference implementations for developers to adapt for their specific hardware and operating systems (e.g., Windows Embedded CE). Media Transfer Protocol Porting Kit
The software component on the device that receives and processes requests from the "initiator" (usually a PC). Porting Kit Installation (PC-Side) MTP allows the device to initiate events (e