docs: def is_available(self):
          """
          Return True if the connection to the host and port is successful.
  
          @return: bool
          """
          if self.scheme in NOOP_PROTOCOLS:
              return True
  
          if not self.port:
              raise RuntimeError('port is required')
  
          s = socket.socket()
          try:
              s.connect((self.host, self.port))
          except Exception:
              return False
          else:
              return True