code: public Set<DeviceAnnouncement> findUnreachablePlayers() {
          ensureRunning();
          Set<DeviceAnnouncement> result = new HashSet<DeviceAnnouncement>();
          for (DeviceAnnouncement candidate: DeviceFinder.getInstance().getCurrentDevices()) {
              if (!Util.sameNetwork(matchedAddress.getNetworkPrefixLength(), matchedAddress.getAddress(), candidate.getAddress())) {
                  result.add(candidate);
              }
          }
          return Collections.unmodifiableSet(result);
      }
docs: Checks if we can see any players that are on a different network than the one we chose for the Virtual CDJ.
  If so, we are not going to be able to communicate with them, and they should all be moved onto a single
  network.
  
  @return the device announcements of any players which are on unreachable networks, or hopefully an empty list
  @throws IllegalStateException if we are not running