1. A method of saving energy in a mobile device client running an application in synchronous communication with an application server comprising the steps of: providing a data pushing operation over a universal supplementary services data (USSD) channel from the application server to the mobile device client; and initiating a data pulling operation over an internet protocol (IP) channel by the mobile device client, in response to the pushing operation, wherein the providing step includes a pushing operation which includes sending from the application server to the mobile device client a notification of change pertaining to the application, and the initiating step includes the mobile device client initiating a transfer of application data in response to the notification.