A network system that performs network connection between devices conforming to a predetermined communication standard is disclosed. The system includes client devices including first network starting units that present first identification information including an identifier decided in advance and designating a first network and start the first network and a server. The server includes a reading unit that reads the first identification information, an option presenting unit that presents, as an option of a network connection destination, a client device including the first identification information read by the reading unit, a first network joining unit that joins the first network when the option is selected, and a transmitting unit that transmits, in the first network, a communication encryption key for joining a second network and second identification information designating the second network to the selected client device.