title: docker ps shows different ports than nmap
body: <p><code>docker ps</code> says there are three ports forwarded:</p>
  
  <pre><code>CONTAINER ID        IMAGE                        COMMAND                  CREATED             STATUS              PORTS                                                      NAMES
  06584d4ad44e        quay.io/coreos/etcd:v3.1.8   "etcd -name etcd01..."   2 days ago          Up 3 minutes        0.0.0.0:2379-2380-&gt;2379-2380/tcp, 0.0.0.0:4001-&gt;4001/tcp   etcd01
  </code></pre>
  
  <p>But <code>nmap -sT 127.0.0.1</code> can only find the <code>4001</code>:</p>
  
  <pre><code>Starting Nmap 7.40 ( https://nmap.org ) at 2017-06-13 00:06 CEST
  Nmap scan report for localhost (127.0.0.1)
  Host is up (0.0011s latency).
  Not shown: 969 closed ports, 30 filtered ports
  PORT     STATE SERVICE
  4001/tcp open  newoak
  </code></pre>
  
  <p>How comes? Can I verify if the ports are there in another way?</p>