title: Connection refused when adding shard in mongoDB
body: <p>I followed the <a href="https://www.digitalocean.com/community/tutorials/how-to-create-a-sharded-cluster-in-mongodb-using-an-ubuntu-12-04-vps" rel="nofollow noreferrer">Digital Ocean tutorial</a> to create a basic sharded cluster in MongoDB with 1 query router,1 config server and 2 shards without replication on the Virtual box in Ubuntu 16.04. I have successfully established the connection between Query Router and Config server according to the tutorial provided but I am getting the error </p>
  
  <pre><code>   { "ok" : 0, "errmsg" : "Connection refused", "code" : 6 }
  </code></pre>
  
  <p>when I run <strong>sh.addShard("ip:port")</strong>. Can someone point what wrong I have been doing?
  PS: I have bindIP as 0.0.0.0 on all my nodes.</p>