When a communication link is disconnected during a printing operation of a print job due to deteriorated radio wave conditions, a printer can prevent and/or reduce incorrect print or other malfunction occurring in response to a print control command included in the print job. Furthermore, in a state monitor function of a peripheral apparatus, when establishment or disconnection of the communication link is unclear due to deteriorated radio wave conditions, the monitor does not fall into an uncontrollable state. A port monitor (PM), controlling a communication interface, confirms a state of the communication interface. A language monitor (LM), controlling a peripheral apparatus, confirms a state of the communication interface. Communications with the peripheral apparatus can be performed based on a state confirmation result of the LM. Furthermore, a transmission buffer is cleared in response to disconnection of the communications.