Patent ID: 7200366

Claim:
A data communication apparatus including a sending unit and a receiving unit to communicate a radio signal light as a carrier wave to a plurality of similar data communication devices, comprising: a discrimination data generation unit configured to generate discrimination data of its device through said sending unit; a direct communicatable device memory configured, when said receiving unit receives discrimination data sent from another device, to store the discrimination data of the other device as a direct communicatable device; a direct communicatable device list generation unit configured to generate a direct communicatable device list including the discrimination data stored in said direct communicatable device memory, and to send the direct communicatable device list with the discrimination data of its device through said sending unit; an indirect communicatable device memory configured, when said receiving unit receives a direct communicatable device list sent from the other device, to store the direct communicatable device list sent from the other device as an indirect communicatable device list in relation to the discrimination data of the other device; and a user data processing unit configured to select the discrimination data as a destination address from the discrimination data stored in said direct communicatable device memory and said indirect communicatable device memory, and to send data with the destination address through said sending unit.