A port monitor program to transmit data about a print job generated by a printer driver to an image forming apparatus includes reading the data about the print job that is generated by the printer driver and spooled by a spooler; determining whether an authentication process associated with restriction of printing is to be performed for the readout data about the print job; submitting an authentication request to an external server over a network to acquire functional restriction information used for the restriction of printing from the server if it is determined that the authentication process is to be performed; and determining how the print job is restricted on the basis of the functional restriction information acquired from the server.