return a list of connected hosts and the number of connections
        to each.  [('foo.com:80', 2), ('bar.org', 1)]

def open_connections(self):
        """return a list of connected hosts and the number of connections
        to each.  [('foo.com:80', 2), ('bar.org', 1)]"""
        return [(host, len(li)) for (host, li) in self._cm.get_all().items()]