title: docker container with multiple tcp ports
body: <p>I created a docker container based on the github link - <a href="https://github.com/wurstmeister/kafka-docker" rel="nofollow noreferrer">https://github.com/wurstmeister/kafka-docker</a></p>
  
  <p>and noticed 3 ports being displayed and one port being mapped to the host.</p>
  
  <p>I understand port 2181 which is been exposed from the container to the host system.</p>
  
  <p>but what are these 3 ports - 22/tcp, 2888/tcp, 3888/tcp ..If these are not exposed to the host system why they are being displayed.</p>
  
  <pre><code>a5779d08be33        wurstmeister/zookeeper                                                             "/bin/sh -c '/usr/..."   40 minutes ago      Up 3 minutes        22/tcp, 2888/tcp, 3888/tcp, 0.0.0.0:2181-&gt;2181/tcp   kafkadocker_zookeeper_1
  </code></pre>