PURPOSE: To prevent such a state that an empty capacity is insufficient after waiting in a long time, at the time of writing a file with a large capacity.

CONSTITUTION: This system is equipped with a means which inputs the information of a file name and a file size from a client machine 1 to a first packet, and transmits it to a server machine 2, an empty capacity judging means which judges whether or not the necessary empty capacity is present in the server machine 2 for writing the file from the information of the first packet transmitted by the above-mentioned means, a means which inputs information obtained at the time of judging that the necessary empty capacity is absent by the empty capacity judging means to a second packet, and transmits it to the client machine 1, and a means which stops the transmission of the file from the client machine 1 to the server machine 2 based on the information of the second packet transmitted by the above-mentioned means.