nanomsg - nanomsg is a socket library that provides several common communication patterns.
ZeroMQ - ZeroMQ is a high-performance asynchronous messaging library.
D-Bus - D-Bus is a message bus system, a simple way for applications to talk to one another.
RabbitMQ - RabbitMQ is an open source message broker software.
NSQ - A realtime distributed messaging platform.
mosquitto - Eclipse Mosquitto is an open source (EPL/EDL licensed) message broker that implements the MQTT protocol versions 5.0, 3.1.1 and 3.1. Mosquitto is lightweight and is suitable for use on all devices