An image forming apparatus and image forming system for communicating with a network via a server are disclosed. The server responds to an inquiry about device information of the image forming apparatus based on device information stored in a memory in a case that the server is in a power saving mode, and also updates device information in the memory upon receiving device information from the image forming apparatus. In addition, the server updates device information in the memory by requesting the image forming apparatus for the device information of the image forming apparatus in a case where the server shifts to the power saving mode. In a case that the device information of the image forming apparatus has changed, the image forming apparatus transmits the changed device information to the server.