RabbitMQ
RabbitMQ implements the Advanced Message Queuing Protocol (AMQP), the standard for business messaging. RabbitMQ supports AMQP 0-9-1, STOMP 1.0 through 1.2, MQTT 3.1.1, AMQP 1.0. Its client implementation can be done in various languages like Python, Java, Ruby, PHP, C#, JavaScript, GO, Elixr.
