code: private void closeClient(Client client) {
          logger.debug("Closing client {}", client);
          client.close();
          openClients.remove(client.targetPlayer);
          useCounts.remove(client);
          timestamps.remove(client);
      }
docs: When it is time to actually close a client, do so, and clean up the related data structures.
  
  @param client the client which has been idle for long enough to be closed