a building automation system comprising a plurality of end devices , at least one communication network , and a server engine comprising a communication state manager for actively managing the state of various devices in building automation system and an associated reconnect manager to reestablish communication with off - line devices . the communication manager and the reconnect manager coordinate the interaction between the server engine and the devices in order to minimizing the load on the communication network , while also working to establish the working state of any of the end devices and to transition off - line to an on - line state .