A communication system including a first terminal device connected to first and second networks, having only a reception function with respect to the first network and transmission and reception functions with respect to the second network, the first network being a radio network according to IEEE 802.11 and the second network being a radio network slower than the first network, and a second terminal device connected to the first and second networks, having at least a transmission function with respect to the first network and transmission and reception functions with respect to the second network is disclosed. In this communication system, the first terminal device carries out a prescribed procedure required in using the first terminal as a receiving side in the first network, by carrying out communications with the second terminal device through the second network, the second terminal device transmits a prescribed information to the first network on behalf of the first terminal device, the prescribed information being an information required to be transmitted to the first network in order for the first terminal device to receive packets through the first network, and the first terminal device receives the packets through the first network.