According to the embodiments, when a communication apparatus is a publisher, a transmission message including a first identifier is transmitted using first transmission power, when the communication apparatus is a subscriber, data of a reception message including the first identifier is stored in a nonvolatile memory, when at least a part of the reception message cannot be received, a repair message for requesting retransmission of the reception message is transmitted from a wireless interface unit using second transmission power, and when there is no response, a repair message is transmitted using third transmission power that is larger than the second transmission power.