A client apparatus comprising: an acquisition unit that is adapted to acquire a plurality of pieces of data that have attributes that are different from each other; an addition unit that, upon a connection with a server apparatus being established, is adapted to add, to each piece of data included in each of a plurality of data sequences that include different pieces of data of the acquired plurality of pieces of data, an identifier that identifies a data group to which the piece of data belongs, the data group being a group consisting of pieces of data that have the same attribute, of a plurality of data groups, and that is associated with the established connection, the identifier uniquely identifies the data group by the association with the established connection; a transmission unit that is adapted to transmit a first data sequence of a plurality of data sequences to the server apparatus via the established connection; and a generation unit that is adapted to generate, upon determining that at least one piece of data of the first data sequence requires re-transmission, a second data sequence including the at least one piece of data previously transmitted in the first data sequence that requires re-transmission; wherein the generation unit is adapted to generate, upon newly acquiring additional pieces of data, a third data sequence of the plurality of data sequences based on the acquired additional pieces of data, the respective identifier being added to each of the first data sequence, the second data sequence, and the third data sequence; and wherein the transmission unit is adapted to transmit the third data sequence of the plurality of data sequences, each of the plurality of data sequences including the pieces of data to which the identifier is added, to the server apparatus via the connection, by inserting, between pieces of data included in the third data sequence of the plurality of data sequences, the second data sequence of the plurality of data sequences. an acquisition unit that is adapted to acquire a plurality of pieces of data that have attributes that are different from each other; an addition unit that, upon a connection with a server apparatus being established, is adapted to add, to each piece of data included in each of a plurality of data sequences that include different pieces of data of the acquired plurality of pieces of data, an identifier that identifies a data group to which the piece of data belongs, the data group being a group consisting of pieces of data that have the same attribute, of a plurality of data groups, and that is associated with the established connection, the identifier uniquely identifies the data group by the association with the established connection; a transmission unit that is adapted to transmit a first data sequence of a plurality of data sequences to the server apparatus via the established connection; and a generation unit that is adapted to generate, upon determining that at least one piece of data of the first data sequence requires re-transmission, a second data sequence including the at least one piece of data previously transmitted in the first data sequence that requires re-transmission; wherein the generation unit is adapted to generate, upon newly acquiring additional pieces of data, a third data sequence of the plurality of data sequences based on the acquired additional pieces of data, the respective identifier being added to each of the first data sequence, the second data sequence, and the third data sequence; and wherein the transmission unit is adapted to transmit the third data sequence of the plurality of data sequences, each of the plurality of data sequences including the pieces of data to which the identifier is added, to the server apparatus via the connection, by inserting, between pieces of data included in the third data sequence of the plurality of data sequences, the second data sequence of the plurality of data sequences. <EOS>