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-record(dns_header, 
    {
     id = 0,       %% ushort query identification number 
     %% byte F0
     qr = 0,       %% :1   response flag
     opcode = 0,   %% :4   purpose of message
     aa = 0,       %% :1   authoritive answer
     tc = 0,       %% :1   truncated message
     rd = 0,       %% :1   recursion desired 
     %% byte F1
     ra = 0,       %% :1   recursion available
     pr = 0,       %% :1   primary server required (non standard)
                   %% :2   unused bits
     rcode = 0     %% :4   response code
    }).
-record(dns_rec,
    {
     header,       %% dns_header record
     qdlist = [],  %% list of question entries
     anlist = [],  %% list of answer entries
     nslist = [],  %% list of authority entries
     arlist = []   %% list of resource entries
    }).

-record(dns_query,
    {
     domain,     %% query domain
     type,        %% query type
     class      %% query class
     }).

-module(zeroconf).
-include("zeroconf.hrl").

-export([open/0,start/0]).
-export([stop/1,receiver/0]).
-export([send/1]).

-define(ADDR, {224,0,0,251}).
-define(PORT, 5353).

open() ->
   {ok,S} = gen_udp:open(?PORT,[{reuseaddr,true}, {ip,?ADDR}, {multicast_ttl,4}, {multicast_loop,false}, binary]),
   inet:setopts(S,[{add_membership,{?ADDR,{0,0,0,0}}}]),
   S.

close(S) -> gen_udp:close(S).

start() ->
   S=open(),
   Pid=spawn(?MODULE,receiver,[]),
   gen_udp:controlling_process(S,Pid),
   {S,Pid}.

stop({S,Pid}) ->
   close(S),
   Pid ! stop.

receiver() ->
   receive
       {udp, _Socket, IP, InPortNo, Packet} ->
           io:format("~n~nFrom: ~p~nPort: ~p~nData: ~p~n",[IP,InPortNo,inet_dns:decode(Packet)]),
           receiver();
       stop -> true;
       AnythingElse -> io:format("RECEIVED: ~p~n",[AnythingElse]),
           receiver()
   end.