A message transmitting and receiving method according to one aspect is performed by a communication apparatus, the communication apparatus including a middleware unit configured to manage a message published by a publisher in a publish/subscribe system in which a message is exchanged between the publisher and a subscriber via a broker, and a storage unit configured to store a library including functions configured to provide the broker, and includes the steps of performing, by the middleware unit, subscribing on the broker by setting a callback function, and upon receipt of a first message published by a device, passing, by the broker, the first message to the middleware unit by calling the callback function.