title: Cannot connect to a Zookeeper instance from another machine
body: <p>I have a simple Kafka installation running with the default Zookeeper. I can send &amp; consume messages from the same server where it is installed. I can also send messages to the Kafka servers from an external server. But when i try to connect the Kafka consumer from the same external server, I see this error every 20 seconds.</p>
  
  <blockquote>
    <p>[2017-12-13 19:51:28,797] WARN Client session timed out, have not heard from server in 20000ms for sessionid 0x16053254a360001 (org.apache.zookeeper.ClientCnxn)</p>
  </blockquote>
  
  <p>The Zookeeper config file is the default one, with following settings.</p>
  
  <pre><code>dataDir=/tmp/zookeeper
  clientPort=2181
  maxClientCnxns=0
  </code></pre>
  
  <p>Are there any tips to troubleshoot this? Thanks.</p>