An internet terminal, which includes a communication unit for sending and receiving packet data, an encryption unit for encrypting and decrypting packet data, a packet generation unit for generating packet data to be sent to a server apparatus, a protocol determination unit for determining a communication protocol to be used between the internet terminal and the server apparatus, a control request reading unit for reading in packet data and a control request packet that includes a control request, a control unit for receiving control information and controlling the internet terminal or a terminal apparatus accordingly. Further, the internet terminal includes a server certificate authentication unit for authenticating the validity of a server certificate sent by the server apparatus, a client certificate management unit for sending a client certificate to the server apparatus, and a storage unit for storing a terminal ID and other information.