title: Is D-Bus a middleware IPC?
body: <p><a href="https://stackoverflow.com/a/33888439/156458">https://stackoverflow.com/a/33888439/156458</a> says</p>
  
  <blockquote>
    <p>D-Bus didn't used to be a Linux (i.e. kernel) IPC, but an additional
    middleware IPC. But in the course of introduction of <a href="https://en.wikipedia.org/wiki/Systemd" rel="nofollow noreferrer"><code>systemd</code></a>,
    D-Bus became for several Linux distributions a part of the basic
    system.</p>
  </blockquote>
  
  <p><a href="https://en.wikipedia.org/wiki/D-Bus#History_and_adoption" rel="nofollow noreferrer">Wikipedia</a> says D-BUS is a "IPC daemon".</p>
  
  <p>Does D-Bus count as </p>
  
  <ul>
  <li><p><a href="https://en.wikipedia.org/wiki/Message-oriented_middleware" rel="nofollow noreferrer">Message-oriented_middleware</a>, or</p></li>
  <li><p><a href="https://en.wikipedia.org/wiki/Message_queue" rel="nofollow noreferrer">Message queue</a>?</p></li>
  </ul>
  
  <p>I heard Zeromq, RabbitMQ, Kafka are also middleware for IPC purposes.
  Are Zeromq, RabbitMQ, Kafka provided at the same level as D-Bus (above  the level of Linux IPC methods)? <a href="https://lists.freedesktop.org/archives/dbus/2010-August/013216.html" rel="nofollow noreferrer">Some</a> compared ZeroMQ to D-Bus, so I was wondering if they are alternative to each other?</p>