An electronic device comprising: - a main system that has a normal state and an energy-saving state in which less energy is consumed than that in the normal state; - a data retaining unit that is configured to store packets; - a subsystem that is configured to execute transmission and reception of packets to and from an external apparatus; and - an operation unit that is an input device via which a user inputs various operations, wherein the subsystem is further configured to store a main dedicated specific packet that is specific type data of main dedicated packets which are packets for which the subsystem cannot generate a response packet based on the communication protocol and the content of the packet and which are therefore required to be processed by the main system in the data retaining unit, if the subsystem receives said main dedicated specific packet from an external apparatus while the main system is in the energy-saving state, wherein the subsystem is further configured to return the main system to the normal state and to cause the main system to process the main dedicated specific packet stored in the data retaining unit and a main dedicated packet other than the main dedicated specific packet, if the subsystem receives the main dedicated packet other than the main dedicated specific packet from an external apparatus while the main system is in the energy-saving state, wherein if the main system returns to the normal state based on an instruction from the subsystem, a process for a main dedicated specific packet or processes for main dedicated packets performed by the main system is to be performed on only a main dedicated specific packet stored in the data retaining unit at a point in time when the main system returns to the normal state, characterized in that after the main system is in the normal state based on an instruction of the subsystem, the subsystem causes the data retaining unit to store a main dedicated specific packet received from an external apparatus, and wherein the main system is configured: - to transition to the energy-saving state, if a process for the main dedicated packet ends after the main system has been returned to the normal state based on an instruction from the subsystem; and - to transition to the energy-saving state, if no operation being input via the operation unit has continued for not less than a certain time period after the main system has been returned to the normal state due to a cause other than the instruction from the subsystem. - a main system that has a normal state and an energy-saving state in which less energy is consumed than that in the normal state; - a data retaining unit that is configured to store packets; - a subsystem that is configured to execute transmission and reception of packets to and from an external apparatus; and - an operation unit that is an input device via which a user inputs various operations, - to transition to the energy-saving state, if a process for the main dedicated packet ends after the main system has been returned to the normal state based on an instruction from the subsystem; and - to transition to the energy-saving state, if no operation being input via the operation unit has continued for not less than a certain time period after the main system has been returned to the normal state due to a cause other than the instruction from the subsystem.