anchor.diff:  %% ----------------------------------------------------------------------------
   %% internal
   %% ----------------------------------------------------------------------------
  -
  -%% @private Generic MO processing
  -callback(SrcAddr, DstAddr, 0, Message, {Mod, Fun}, _DR) ->
  -  apply(Mod, Fun, [SrcAddr, DstAddr, Message]);
  -
  -%% @private Generic DR processing
  -callback(SrcAddr, DstAddr, 4, Message, _MO, {Mod, Fun}) ->
  -  DeliveryReceipt = dr_to_map(Message),
  -  apply(Mod, Fun, [SrcAddr, DstAddr, DeliveryReceipt]).
   
   %% @private
   normalize_encoding(8, Message) ->
  
positive.code: }).
  
  -record(state, {
    connected = false :: boolean(), 
    seq_num   =  1    :: integer(),
    binding   =  0    :: integer(),
    status    = -1    :: integer(),
    from_list = #{}   :: map(),
    callback_mo       :: {atom(), atom()},
    callback_dr       :: {atom(), atom()},
    socket            :: port(),
    tref              :: {integer(), reference()}
  }).
  
  %% ----------------------------------------------------------------------------
  
negative.code: -include("commands.hrl").
  -include("command_statuses.hrl").
  
  -record(mo_part, {
    max_parts :: integer(),
    src_addr  :: iodata(),
    dst_addr  :: iodata(),
    messages  :: [iodata()]
  }).
  
  -record(conn_state, {
    host              :: iodata(),
    port              :: integer(),
  