A relay apparatus configured to be used in a system comprising a plurality of image processing apparatuses, a server apparatus; and the relay apparatus, wherein the image processing apparatuses are connected to a network through a router having a firewall function; the relay apparatus comprising: a network interface configured to perform communication with the image processing apparatuses and the server apparatus through the network; and a processor; wherein the processor is configured to cause the relay apparatus: to receive, via the network interface, server request information transmitted by the server apparatus, the server request information representing a request to the image processing apparatus; in response to receiving, via the network interface, establishment request information, transmitted by the image processing apparatus via the network interface through the router, to establish a session between the relay apparatus and the image processing apparatus according to a session establishment type first protocol for enabling server-push for transmitting the received server request information to the image processing apparatus; and in a case the establishment request information has been received when the server request information is received, to transmit, via the network interface, the received server request information to the image processing apparatus through the router using the session establishment type first protocol for enabling server-push; wherein the first protocol is extensible Messaging and Presence Protocol over Bidirectional-streams Over Synchronous HTTP. a network interface configured to perform communication with the image processing apparatuses and the server apparatus through the network; and a processor; wherein the processor is configured to cause the relay apparatus: to receive, via the network interface, server request information transmitted by the server apparatus, the server request information representing a request to the image processing apparatus; in response to receiving, via the network interface, establishment request information, transmitted by the image processing apparatus via the network interface through the router, to establish a session between the relay apparatus and the image processing apparatus according to a session establishment type first protocol for enabling server-push for transmitting the received server request information to the image processing apparatus; and in a case the establishment request information has been received when the server request information is received, to transmit, via the network interface, the received server request information to the image processing apparatus through the router using the session establishment type first protocol for enabling server-push; wherein the first protocol is extensible Messaging and Presence Protocol over Bidirectional-streams Over Synchronous HTTP. to receive, via the network interface, server request information transmitted by the server apparatus, the server request information representing a request to the image processing apparatus; in response to receiving, via the network interface, establishment request information, transmitted by the image processing apparatus via the network interface through the router, to establish a session between the relay apparatus and the image processing apparatus according to a session establishment type first protocol for enabling server-push for transmitting the received server request information to the image processing apparatus; and in a case the establishment request information has been received when the server request information is received, to transmit, via the network interface, the received server request information to the image processing apparatus through the router using the session establishment type first protocol for enabling server-push; wherein the first protocol is extensible Messaging and Presence Protocol over Bidirectional-streams Over Synchronous HTTP.