Abstract: An interactive system includes a server system, a modem, and a terminal device. The server system provides service content that may include a video stream and selection items. The modem connects to the server system via a network. The modem can transmit information according to priority levels. The terminal device connects to the modem. The terminal device is configured to assign a highest transmission priority level to a selection result of a selected item selected by a user from the selection items. The server system is configured to provide response information according to the selection result and transmit the response information in a unicast manner.