To provide a communication system capable of autonomously starting a specific communication event by a user's operation on a peripheral device side in spite of the fact that the issuing direction of commands conducting execution of communication events is regulated to one direction from a PC side to the peripheral device side.

A host device issues a file type request command to the peripheral device, receives file type information of a file type selected by a user in the peripheral device from the peripheral device, and sets the file type for performing data access. The host device issues a trigger report request command toward the peripheral device according to a main communication protocol. When a storage medium is installed to the peripheral device, the host device receives trigger generation report information from the peripheral device and transmits data of a file of the set file type to the host device, when presence of the peripheral device-side trigger is determined, to start application software.

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