We present two protocols one of which supports the publication by sensors in a sensor-network of messages on a named topic, the other that allows sensors to subscribe to messages on a named topic. We separate the publish and subscribe functions into different protocols as it is not necessary for a given device to support both. The publication protocol is designed for management systems in which nodes take readings from a sensor and transmit them to monitoring applications while the subscription protocol is for actuating systems in which the state of certain nodes is changed by control applications. The protocols use cross-layer optimization techniques for reducing transmissions within the messaging layer of the sensor-network. We show that the path characteristics of such network are highly variable leading to frequent topology changes motivating our description of the protocols which can function even over fluctuating network topologies. Finally, we use simulation to compare the actuation protocol with an epidemic approach, showing that our protocol is more efficient when the topics that the nodes are interested in are non-uniform.