anchor.diff:  test_flush(Sock) ->
       {ok, works, undefined} = send_recv(Sock, undefined, undefined,
                               #mc_header{opcode = ?FLUSH}, #mc_entry{}, works).
  -
  
positive.code: 
  %% @doc Receive binary data of specified number of bytes length.
  recv_data(_, 0)           -> {ok, <<>>};
  recv_data(Sock, NumBytes) -> gen_tcp:recv(Sock, NumBytes).
  
  % -------------------------------------------------
  
  
negative.code: -export([bin/1, recv/2, send/4]).
  
  -define(FLUSH_TIMEOUT, 5000).
  -define(RECV_TIMEOUT, 5000).
  
  %% Functions to work with memcached binary protocol packets.
  
  