code: void notifyListenersNetworkReachable() {
          // NOTE: synchronized(listener) causes deadlock with listeners and Replicator.lock.
          final Set<NetworkReachabilityListener> copy = new HashSet<>(listeners);
          for (NetworkReachabilityListener listener : copy) {
              if (listener != null) { listener.networkReachable(); }
          }
      }
docs: Notify listeners that the network is now reachable