title: How to get the opened port (firewall) of an instance in GCP using gcloud?
body: <p>For example, I have an instance named <code>test</code>, now I need to know which port is opened for this instance. How do I do it in command line using <code>gcloud</code>?</p>
  
  <p>Not the port opened inside the instance, but the Firewall attached to this instance.</p>