A communication system includes a device and a server connected to the Internet, which transfers communications between the device and a terminal connectable to the Internet via the server. The device periodically transmits a notice packet to the server. The server transmits a connection request packet to the device in reply to the notice packet when a transfer to the device is requested from the terminal. The device transmits a TCP connection request to the server when receiving the connection request packet from the server. The server accepts the TCP connection request transmitted from the device to the server in reply to the connection request packet, to establish the TCP connection. Thus, the server transfers communications between the terminal and the device on the TCP connection after the TCP connection is established.