A method for controlling a mobile system including a first terminal, and a second terminal, the method comprising: transmitting a request message to the second terminal from the first terminal, based on a user input applied to the first terminal; determining whether the transmitted request message satisfies a preset first condition by the second terminal; processing s a control command corresponding to the transmitted request message by the second terminal, based on the determination result with respect to the first condition; transmitting a response message reflecting a result of the processing, to the first terminal from the second terminal; determining whether the transmitted response message satisfies a preset second condition, by the first terminal; and processing a control command corresponding to the transmitted response message by the first terminal, based on a determination result with respect to the second condition, wherein the request message and the response message are formed by using a short message service, SMS, and contents of the request message and the response message are formed based on a preset protocol, wherein the determining whether the transmitted request message satisfies a preset first condition includes determining whether the same request message has already been received, and wherein the determining whether the transmitted response message satisfies a preset second condition includes determining whether the same response message has already been received, wherein the determining whether the same request message has already been received, comprises generating index information of the received request message and comparing the index information of the received request message with index information pre-generated before the request message is received, wherein the control command corresponding to the transmitted request message comprises a command for processing setting information in order to register the first terminal as a guardian terminal of the second terminal to set a control right of the first terminal, and wherein if the first terminal is registered as a guardian terminal for the second terminal, the index information in the response message is set by the second terminal to correspond to that of the request message. transmitting a request message to the second terminal from the first terminal, based on a user input applied to the first terminal; determining whether the transmitted request message satisfies a preset first condition by the second terminal; processing s a control command corresponding to the transmitted request message by the second terminal, based on the determination result with respect to the first condition; transmitting a response message reflecting a result of the processing, to the first terminal from the second terminal; determining whether the transmitted response message satisfies a preset second condition, by the first terminal; and processing a control command corresponding to the transmitted response message by the first terminal, based on a determination result with respect to the second condition, wherein the request message and the response message are formed by using a short message service, SMS, and contents of the request message and the response message are formed based on a preset protocol, wherein the determining whether the transmitted request message satisfies a preset first condition includes determining whether the same request message has already been received, and wherein the determining whether the transmitted response message satisfies a preset second condition includes determining whether the same response message has already been received, wherein the determining whether the same request message has already been received, comprises generating index information of the received request message and comparing the index information of the received request message with index information pre-generated before the request message is received, wherein the control command corresponding to the transmitted request message comprises a command for processing setting information in order to register the first terminal as a guardian terminal of the second terminal to set a control right of the first terminal, and wherein if the first terminal is registered as a guardian terminal for the second terminal, the index information in the response message is set by the second terminal to correspond to that of the request message.