code: func (process *TeleportProcess) importOrCreateListener(listenerType, address string) (net.Listener, error) {
  	l, err := process.importListener(listenerType, address)
  	if err == nil {
  		process.Infof("Using file descriptor %v %v passed by the parent process.", listenerType, address)
  		return l, nil
  	}
  	if !trace.IsNotFound(err) {
  		return nil, trace.Wrap(err)
  	}
  	process.Infof("Service %v is creating new listener on %v.", listenerType, address)
  	return process.createListener(listenerType, address)
  }
docs: // importOrCreateListener imports listener passed by the parent process (happens during live reload)
  // or creates a new listener if there was no listener registered