docs: function Hub() {
          log.info("instantiate hub");
          // get non-ambiguous this
          var self = this;
          // Call parent constructor
          Hub.super_.call(self);
          // Internal structures
          self._subscribers = {};
          // subsribers is { source._id: {'source': source, patterns: [pattern*]}}
          self._transport = undefined;
          self._closed = false;
          // state listeners
          self.once('close', function handleClosed() {
              self._closed = true;
          });
          // Constructor.  Return undefined.
          return undefined;
      }