A communication system includes a plurality of devices, a plurality of communication relay apparatuses, and a management server. If the management server that has received from a cloud server a request to access a specific device has no communication session with a specific communication relay apparatus that has control over the specific device, the management server transmits a tunnel connection request to a substitute apparatus (another communication relay apparatus different from the specific communication relay apparatus) via a communication session between the substitute apparatus and the management server. The substitute apparatus transfers the tunnel connection request to the specific communication relay apparatus and causes the specific communication relay apparatus to return from a power saving mode. The specific communication relay apparatus then establishes tunnel communication with the cloud server on the basis of the tunnel connection request to relay communication between the cloud server and the specific device.