anchor.diff:                         version=Version,
                          headers=Headers,
                          next_packet_id=1},
  -            inet:setopts(Sock, [{active, once}]),
  +            inet:setopts(Socket, [{active, once}]),
               {ok, State2};
           {error, Reason} ->
               {stop, Reason}
  
positive.code: -behavior(gen_server).
  
  -record(state, {
            sock :: gen_tcp:socket(),
            options :: [connect_option()],
            next_packet_id :: packet_id(),
            headers :: [{binary(), binary()}],
  
negative.code: -spec init_req(State) -> {ok, State} | {stop, Reason} when
        State :: state(),
        Reason:: error_reason().
  init_req(#state{socket=Socket}=State) ->
      Packet = construct_init_req(),
      case gen_tcp:send(Socket, Packet) of
          ok ->
              init_res(State);
          {error, Reason} ->
  