A communication system comprising: an image processing apparatus; a supporting apparatus capable of providing remote support to the image processing apparatus; and a management server configured to associate the image processing apparatus with the supporting apparatus for providing the remote support to the image processing apparatus to manage the image processing apparatus and the supporting apparatus, wherein the image processing apparatus includes: a receiving means configured to receive a remote support service start request from a user; a request means configured to, if the remote support service start request is received by the receiving means (S402; S1406), request a relay server to allocate relay information (S403; S1407) for communication via the relay server; and a first notification means configured to notify (S407; S1411) the management server of the relay information allocated by the relay server in response to the request from the request means, wherein the management server includes a second notification means configured to notify (S408; S1412) the supporting apparatus managed in association with the image processing apparatus of the relay information notified by the first notification means, wherein the image processing apparatus and the supporting apparatus are configured to transmit a POST request in the HTTP format of support data to the relay server using the relay information, the support data being buffered in the relay server according to the POST request, wherein the image processing apparatus and the supporting apparatus are configured to transmit a GET request in the HTTP format to the relay server using the relay information, and to receive the support data buffered in the relay server from the relay server in response to the GET request, and wherein the image processing apparatus further includes a determination means configured to determine whether a monitoring service is being received from the management server, and wherein the first notification means is configured to notify the management server of the relay information if the determination means determines that the monitoring service is being received, whereas the first notification means is configured to notify the supporting apparatus of the relay information if the determination means determines that the monitoring service is not being received. an image processing apparatus; a supporting apparatus capable of providing remote support to the image processing apparatus; and a management server configured to associate the image processing apparatus with the supporting apparatus for providing the remote support to the image processing apparatus to manage the image processing apparatus and the supporting apparatus, wherein the image processing apparatus includes: a receiving means configured to receive a remote support service start request from a user; a request means configured to, if the remote support service start request is received by the receiving means (S402; S1406), request a relay server to allocate relay information (S403; S1407) for communication via the relay server; and a first notification means configured to notify (S407; S1411) the management server of the relay information allocated by the relay server in response to the request from the request means, a receiving means configured to receive a remote support service start request from a user; a request means configured to, if the remote support service start request is received by the receiving means (S402; S1406), request a relay server to allocate relay information (S403; S1407) for communication via the relay server; and a first notification means configured to notify (S407; S1411) the management server of the relay information allocated by the relay server in response to the request from the request means, wherein the management server includes a second notification means configured to notify (S408; S1412) the supporting apparatus managed in association with the image processing apparatus of the relay information notified by the first notification means, wherein the image processing apparatus and the supporting apparatus are configured to transmit a POST request in the HTTP format of support data to the relay server using the relay information, the support data being buffered in the relay server according to the POST request, wherein the image processing apparatus and the supporting apparatus are configured to transmit a GET request in the HTTP format to the relay server using the relay information, and to receive the support data buffered in the relay server from the relay server in response to the GET request, and wherein the image processing apparatus further includes a determination means configured to determine whether a monitoring service is being received from the management server, and wherein the first notification means is configured to notify the management server of the relay information if the determination means determines that the monitoring service is being received, whereas the first notification means is configured to notify the supporting apparatus of the relay information if the determination means determines that the monitoring service is not being received.