Abstract: A printing system has a host apparatus (information processing apparatus) and a printing apparatus (output apparatus) for performing a printing operation in accordance with data supplied from the host apparatus. A plurality of communication channels are provided between the host apparatus and the printing apparatus. The numbers of packets transmittable and receivable in each communication channel are checked. When there is no packet transmittable to the printing apparatus from the host apparatus, the host apparatus issues a request, after a lapse of a predetermined delay time, to instruct the printing apparatus to inform the host apparatus of the number of valid packets. The delay time for issuing a subsequent request to the printing apparatus for the notification of the number of valid packets is adjusted in accordance with the previous delay time and the number of packets obtained in response to the previous request from the host apparatus.