A client apparatus, after inputting a print job to a print service server apparatus, delivers a multicast message including information relating to an execution apparatus that executes the print job and information relating to a proxy apparatus managed by the print service server apparatus that manages the execution apparatus. When an image output apparatus receives the message, the image output apparatus determines whether the apparatus itself executes the print job or requests the proxy apparatus to execute the print job for the apparatus itself, based on a content of the message. If the image output apparatus determines to request the proxy apparatus to execute the print job for the apparatus itself, the image output apparatus requests the proxy apparatus to execute the print job.