title: Couldn't connect to trainer on port 5004 using API version API-13 when using Unity3D ML-Agents
body: <p>I'm using Unity3D ML-Agents and when running examples of multiple clones inside(3DBall for example), there is a message in the console says:</p>
  
  <blockquote>
    <p>Couldn't connect to trainer on port 5004 using API version API-13.
    Will perform inference instead. UnityEngine.Debug:Log(Object)
    MLAgents.Academy:InitializeEnvironment() (at
    Assets/ML-Agents/Scripts/Academy.cs:228)
    MLAgents.Academy:LazyInitialization() (at
    Assets/ML-Agents/Scripts/Academy.cs:147) MLAgents.Agent:OnEnable() (at
    Assets/ML-Agents/Scripts/Agent.cs:255)</p>
  </blockquote>
  
  <p>I tried to turn off the firewall but it didn't work.
  How can I solve it?</p>
  
  <p>The version I'm using is</p>
  
  <pre><code>Unity 2018.4.14f1, 
  ml-agents: 0.13.0,   
  ml-agents-envs: 0.13.0,  
  Communicator API: API-13,   
  TensorFlow: 1.7.1
  </code></pre>