An image forming apparatus is made to be usable by a greater number of portable terminal apparatuses than a limited number of terminals. In an image forming system, a first portable terminal apparatus is registered in the image forming apparatus so as to be able to transmit job requests to the image forming apparatus using a specified peer-to-peer communication method, however a second portable terminal apparatus is not registered. The image forming apparatus, (a) reads by an image reading apparatus a device ID of the first portable terminal apparatus and a device ID of the second terminal apparatus. Then, the image forming apparatus, (b) transmits the device ID of the second portable terminal apparatus to the first portable terminal apparatus using the peer-to-peer communication method. The first portable terminal apparatus, (a) correlates the received device ID of the second portable terminal apparatus with the first portable terminal apparatus, and registers the device ID in the server. Then, the first portable terminal apparatus, (b) receives a job request that is issued by the second portable terminal apparatus, and transmits that job request to the image forming apparatus using the peer-to-peer communication method. The server transmits the job request received from the second portable terminal apparatus to the first portable terminal apparatus that is correlated with the device ID of that second portable terminal apparatus.