anchor.diff:      {reply, Result, State};
   
   
  +handle_call({history, _Count}, _From, State) ->
  +    History = State#state.history,
  +    {reply, {ok, History}, State};
   
   handle_call({leave, ClientPid}, _From, State) ->
       Clients = State#state.clients,
  
positive.code: 
  -define(TTL, 5000).
  -define(IDEL_TIMEOUT, 600000).
  
  %% API.
  
  
negative.code:     catch _:_ ->
          {{error, <<"Error occured when deploy message!">>}, State}
      end,
  	{noreply, NewState#state{history=NewHistory}};
  
  handle_cast(_Msg, State) ->
  	{noreply, State}.
  