Transmitting device, receiving device, and file forwarding system

A transmitting device, a receiving device, and a file forwarding system for effectively executing processes related to a file forwarding even if the file forwarding is interrupted for a longtime in the file forwarding system in which the transmitting device voluntarily forwards a file to the receiving device. In a file forwarding system, a sink device, which is a receiving device, stores file data, which constitutes a file, received from a source device, which is a transmitting device, and, when receiving an inquiry about the size of the stored data from the source device, notifies the source device of the size of the stored data. Having detected an interruption of the file forwarding, the source device inquires the sink device of the size of the stored data. Further, the source device transmits file data, which constitutes the remaining part of the file, in accordance with the size of the stored data notified of by the sink device in response to that inquiry.