According to an aspect of the invention, a data communication system includes first and second data communication apparatuses, and a data server. The first data communication apparatus receives first data transmitted from a data transmitting apparatus through a unidirectional communication, receives second data transmitted from the data server through a bidirectional communication, and generates output data based on at least one of the first and second data. The second data communication apparatus receives the second data transmitted from the data transmitting apparatus through a unidirectional communication, and transmits the second data to the data server through a bidirectional communication.
