anchor.diff:                            end,
                      Recv = fun(Sock) ->
                                     socket:recvfrom(Sock, 0, nowait)
  +                          end,
  +                   InitState = #{domain => inet,
  +                                 send   => Send,
  +                                 recv   => Recv},
  +                   ok = api_a_send_and_recv_udp(InitState)
  +           end).
  +
  +
  +
  +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  +
  +%% Basically send and receive on an IPv4 UDP (dgram) socket using
  +%% sendto and recvfrom. But we try to be async. That is, we use
  +%% the 'nowait' value for the Timeout argument (and await the eventual
  +%% select message). Note that we only do this for the recvfrom,
  +%% since its much more difficult to "arrange" for sendto.
  +%%
  +api_a_sendmsg_and_recvmsg_udp4(suite) ->
  +    [];
  +api_a_sendmsg_and_recvmsg_udp4(doc) ->
  +    [];
  +api_a_sendmsg_and_recvmsg_udp4(_Config) when is_list(_Config) ->
  +    ?TT(?SECS(5)),
  +    tc_try(api_a_sendmsg_and_recvmsg_udp4,
  +           fun() ->
  +                   Send = fun(Sock, Data, Dest) ->
  +                                  MsgHdr = #{addr => Dest,
  +                                             %% ctrl => CMsgHdrs,
  +                                             iov  => [Data]},
  +                                  socket:sendmsg(Sock, MsgHdr)
  +                          end,
  +                   Recv = fun(Sock) ->
  +                                  case socket:recvmsg(Sock, nowait) of
  +                                      {ok, #{addr  := Source,
  +                                             iov   := [Data]}} ->
  +                                          {ok, {Source, Data}};
  +                                      {ok, _} = OK ->
  +                                          OK;
  +                                      {error, _} = ERROR ->
  +                                          ERROR
  +                                  end
                             end,
                      InitState = #{domain => inet,
                                    send   => Send,
  
positive.code: 
           %% *** API async ***
           api_a_sendto_and_recvfrom_udp4/1,
           %% api_a_sendmsg_and_recvmsg_udp4/1,
           %% api_a_send_and_recv_tcp4/1,
           %% api_a_sendmsg_and_recvmsg_tcp4/1,
  
  
negative.code: 
  api_async_cases() ->
      [
       api_a_sendto_and_recvfrom_udp4,
       api_a_sendmsg_and_recvmsg_udp4%%,
       %% api_a_send_and_recv_tcp4,
       %% api_a_sendmsg_and_recvmsg_tcp4
      ].
  