anchor.diff:  
   % id is Id -> {Client, Cookie}
   % cookie is Cookie -> Id
  --record(state, {id, cookie}).
  +% tables is orddict of table_id -> table
  +% table_cnt counter for next id
  +-record(state, {id, cookie, tables, table_cnt}).
   
   % Public:
   start() ->
  
positive.code:     {ok, Client} -> {reply, {ok, Client}, State};
      error -> {reply, {error, invalid}, State}
    end;
  
  handle_call(Request, _From, State) ->
    io:format("~w received unknown call ~p~n",
  
negative.code: get_client_by_cookie(Cookie) ->
    gen_server:call({global, ?MODULE}, {get_client_by_cookie, Cookie}).
  
  create_table() ->
    gen_server:call({global, ?MODULE}, {create_table}).
  
  % gen_server:
  init([]) ->
    {ok, #state{id=orddict:new(),
                cookie=orddict:new(),
                tables = [],
                table_cnt = 0}}.
  
  % TODO: Set monitor on client, clear cookie when dies.
  handle_call({get_client, Id}, _From, State) ->
  