code: private boolean pingSecondaryProtocol(Protocol protocol) {
      try {
        if (protocol != null && protocol.isConnected() && protocol.ping()) {
          return true;
        }
      } catch (Exception e) {
        protocol.close();
  
        if (setSecondaryHostFail()) {
          addToBlacklist(protocol.getHostAddress());
        }
      }
      return false;
    }
docs: Ping secondary protocol. ! lock must be set !
  
  @param protocol socket to ping
  @return true if ping is valid.