code: func (s *PortManager) IsPortAvailable(networks []tcpip.NetworkProtocolNumber, transport tcpip.TransportProtocolNumber, addr tcpip.Address, port uint16, reuse bool) bool {
  	s.mu.Lock()
  	defer s.mu.Unlock()
  	return s.isPortAvailableLocked(networks, transport, addr, port, reuse)
  }
docs: // IsPortAvailable tests if the given port is available on all given protocols.