a server including : a communication unit for wirelessly communicating with a mobile terminal through one of wireless network gateways ; and a processing unit for receiving registration request information from the mobile terminal through the communication unit , executing handoff from one wireless interface to another wireless interface and sending a signal instructing the termination of wireless connection generated by the processing unit to the wireless network gateway through the communication unit to release wireless connection before handoff between the server and the access point when the registration request information indicates the termination of the current wireless connection .