A communication system comprising: a plurality of devices that are provided inside a predetermined LAN; a plurality of communication relay apparatuses that are provided inside the predetermined LAN and relay communication between the plurality of devices and a cloud server provided outside the predetermined LAN; and a management server that is provided outside the predetermined LAN and is adapted to receive from the cloud server an access request to access a specific device among the plurality of devices, wherein the plurality of communication relay apparatuses include: a specific communication relay apparatus that is capable of transitioning to a power saving mode and has control over the specific device, the power saving mode being a mode in which the communication relay apparatus has no communication session with the management server; and a substitute communication relay apparatus that is adapted to receive, in place of the specific communication relay apparatus, a tunnel connection request to establish tunnel connection with the cloud server, via a communication session between the substitute communication relay apparatus and the management server, wherein in a case where the management server has received the access request from the cloud server and there is no communication session between the specific communication relay apparatus and the management server, the management server is adapted to transmit the tunnel connection request to the substitute communication relay apparatus via a communication session between the substitute communication relay apparatus and the management server, the substitute communication relay apparatus that has received the tunnel connection request from the management server is adapted to transfer the tunnel connection request to the specific communication relay apparatus and is adapted to cause the specific communication relay apparatus to return from the power saving mode, and the specific communication relay apparatus that has returned from the power saving mode is adapted to establish tunnel communication with the cloud server in response to the tunnel connection request received from the substitute communication relay apparatus, and is adapted to relay communication between the cloud server and the specific device. a plurality of devices that are provided inside a predetermined LAN; a plurality of communication relay apparatuses that are provided inside the predetermined LAN and relay communication between the plurality of devices and a cloud server provided outside the predetermined LAN; and a management server that is provided outside the predetermined LAN and is adapted to receive from the cloud server an access request to access a specific device among the plurality of devices, a specific communication relay apparatus that is capable of transitioning to a power saving mode and has control over the specific device, the power saving mode being a mode in which the communication relay apparatus has no communication session with the management server; and a substitute communication relay apparatus that is adapted to receive, in place of the specific communication relay apparatus, a tunnel connection request to establish tunnel connection with the cloud server, via a communication session between the substitute communication relay apparatus and the management server, wherein