A wireless network system includes a platform device transmitting a first message including display capability information to at least one device and at least one device transmitting a second message to the platform device in response to the first message. The display capability information includes information on a display space and a display format supportable by the platform device. The second message includes display output information of the at least one device. The display output information includes: information on a display space, a display format, and display contents selected by the at least one device based upon the display capability information; and field type information that indicates characteristics of a field in which the display contents are displayed.