anchor.diff:  
   %% @doc This function is called on incoming data for bridged connections
   -spec conn_bridge(nkpacket:incoming(), up|down, nkport(), conn_state()) ->
  -	{ok, nkpacket:incoming(), conn_state()} | {skip, conn_state()} | 
  +	{ok, nkpacket:incoming(), conn_state()} | {skip, conn_state()} |
   	{stop, term(), conn_state()}.
   
   conn_bridge(Data, _Type, _NkPort, ConnState) ->
  
positive.code: 
  -export([transports/1, default_port/1, resolve_opts/0, naptr/2]).
  -export([conn_init/1, conn_parse/3, conn_encode/3, conn_encode/2, conn_bridge/4,
           conn_timeout/2,
  		 conn_handle_call/4, conn_handle_cast/3, conn_handle_info/3, conn_stop/3]).
  -export([listen_init/1, listen_parse/5, listen_handle_call/4,
  		 listen_handle_cast/3, listen_handle_info/3, listen_stop/3]).
  -export([http_init/4]).
  -export([behavior_info/1]).
  
  
  %% ===================================================================
  %% Behavior
  %% ===================================================================
  
  
  %% @doc No mandatory functions
  behavior_info(callbacks) -> 
  	[];
  behavior_info(_) ->
      undefined.
  
  
  %% ===================================================================
  %% Types
  %% ===================================================================
  
  
  -type listen_state() :: term().
  -type conn_state() :: term().
  -type nkport() :: nkpacket:nkport().
  
  
  %% ===================================================================
  %% Common callbacks
  %% ===================================================================
  
  %% @doc If you implement this function, it must return, for any supported scheme,
  
negative.code: 
  %% @doc This function is called only for UDP transports using no_connections=>true
  -spec listen_parse(inet:ip_address(), inet:port_number(), binary(), nkport(),
  	listen_state()) ->
  	{ok, listen_state()} | {stop, Reason::term(), listen_state()}.
  
  listen_parse(_Ip, _Port, _Msg, _NkPort, ListenState) ->
  	{stop, not_defined, ListenState}.
  