code: def status(self, host=None):
          
          if host is None:
              host_cores = self.host_cores
          else:
              host_cores = [hc for hc in self.host_cores if hc[0] == host]
          lst = []
          for host, _ in host_cores:
              ready = general.socket_ready((host, self.ctrl_port))
              lst.append((host, 'running' if ready else 'not-running'))
          return lst
docs: :returns: a list of pairs (hostname, 'running'|'not-running')