title: how to send message to parent process
body: <p>Can I send message to parent process?</p>
  
  <p>master</p>
  
  <pre><code>var child =child_process.fork();
  
  child.send({msg:msg})
  </code></pre>
  
  <p>child process</p>
  
  <pre><code>process.on('message', function(){
  
  });
  
  // how to send message to parent??
  </code></pre>