The Really Small Message Broker enables messaging to and from tiny devices such as sensors and actuators over networks that might have low bandwidth, high cost, and varying reliability. "Publishers" send messages to the broker, which then distributes the messages to the "subscribers" who have requested to receive those messages.
Really Small Message Broker has a "bridge" that enables connections to other MQTT-capable servers; this bridge allows messages to be passed between Really Small Message Broker instances as well as to other MQTT servers such as Lotus Expeditor micro broker ("Microbroker") and WebSphere MQ. Both Microbroker and Really Small Message Broker can run in embedded systems in order to provide a messaging infrastructure in remote installations and pervasive environments. However, Really Small Message Broker needs about 100 times less memory to run than Microbroker; therefore, it can extend the reach of the MQTT messaging infrastructure further.
MQTT is a machine-to-machine (M2M)/"Internet of Things" connectivity protocol. It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium. For example, it has been used in sensors communicating to a broker via satellite link, over occasional dial-up connections with healthcare providers, and in a range of home automation and small device scenarios. It is also ideal for mobile applications because of its small size, low power usage, minimised data packets, and efficient distribution of information to one or many receivers