Patent ID: 7502316

Claim:
A data receiving apparatus comprising: first receiving means for receiving through a unidirectional channel, segmental data forming an electronic file, or redundant data for restoration of the segmental data from a first data transmitter; restoring means for restoring the electronic file, based on the segmental data or the redundant data received by the first receiving means; location information acquiring means for acquiring location information for specifying a second data transmitter that includes the electronic file; channel establishing means for establishing a bidirectional channel with the second data transmitter when there arises a need for retransmission of all or part of the electronic file; determining means for determining an end of transmission of the segmental data forming the electronic file, or the redundant data for restoration of the segmental data; wait time information acquiring means for acquiring, from a file included in the segmental data received through the unidirectional channel, wait time information for specifying a wait time before establishment of a bidirectional channel, wherein the channel establishing means establishes the bidirectional channel after a wait for a time calculated using the wait time specified by the wait time information acquired by the wait time information acquiring means, and a random number when the determining means determines the end of transmission and the restoring means fails to restore the electronic file; and second receiving means for sending a request for transmission of all or part of the electronic file to the second data transmitter through the bidirectional channel established by the channel establishing means, and for receiving all or part of the electronic file from the second data transmitter through the bidirectional channel.