RabbitMQ - RabbitMQ is an open source message broker software.
ZeroMQ - ZeroMQ is a high-performance asynchronous messaging library.
Apache Kafka - Apache Kafka is an open-source message broker project developed by the Apache Software Foundation written in Scala.
D-Bus - D-Bus is a message bus system, a simple way for applications to talk to one another.
nanomsg - nanomsg is a socket library that provides several common communication patterns.
Apache ActiveMQ - Apache ActiveMQ is an open source messaging and integration patterns server.