mosquitto

MQTT version 3.1 compatible message broker
This is a message broker that supports version 3.1 of the MQ Telemetry
Transport protocol.
.
MQTT provides a method of carrying out messaging using a publish/subscribe
model. It is lightweight, both in terms of bandwidth usage and ease of
implementation. This makes it particularly useful at the edge of the network
where a sensor or other simple device may be implemented using an arduino for
example.