mod_echobot

-module(mod_echobot).
-author('Steven Livingstone-Perez').

-behavior(gen_server).
-behavior(gen_mod).

%% Interface

-export([start_link/2]).

-export([start/2,
  stop/1,
  init/1,
  handle_call/3,
  handle_cast/2,
  handle_info/2,
  terminate/2,
  code_change/3]).

-export([route/3]).

-include("ejabberd.hrl").
-include("logger.hrl").

-define(PROCNAME, ejabberd_mod_bot).
-define(BOTNAME, echo_bot).

%% Implementation

start_link(Host, Opts) ->
  Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
  gen_server:start_link({local, Proc}, ?MODULE, [Host, Opts], []).

start(Host, Opts) ->
  Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
  ChildSpec = {Proc,
    {?MODULE, start_link, [Host, Opts]},
    temporary,
    1000,
    worker,
    [?MODULE]},
  supervisor:start_child(ejabberd_sup, ChildSpec).

stop(Host) ->
  Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
  gen_server:call(Proc, stop),
  supervisor:terminate_child(ejabberd_sup, Proc),
  supervisor:delete_child(ejabberd_sup, Proc).

init([Host, Opts]) ->
  error_logger:info_msg("ECHO_BOT: Starting echo_bot", []),
  %?DEBUG("ECHO_BOT: Starting echo_bot", []),
  % add a new virtual host / subdomain "echo".example.com
  MyHost = gen_mod:get_opt_host(Host, Opts, <<"echo.@HOST@">>),
  ejabberd_router:register_route(MyHost, {apply, ?MODULE, route}),
  {ok, Host}.

handle_call(stop, _From, Host) ->
  {stop, normal, ok, Host}.

handle_cast(_Msg, Host) ->
  {noreply, Host}.

handle_info(_Msg, Host) ->
  {noreply, Host}.

terminate(_Reason, Host) ->
  ejabberd_router:unregister_route(Host),
  ok.

code_change(_OldVsn, Host, _Extra) ->
  {ok, Host}.

% Checks a presence /subscription/ is a part of this.
% we may want to impliment blacklisting / some kind of
% protection here to prevent malicious users
%route(From, #jid{luser = ?BOTNAME} = To, {xmlelement, "presence", _, _} = Packet) ->
route(From, To, {xmlelement, "presence", _, _} = Packet) ->
  case xml:get_tag_attr_s("type", Packet) of
    "subscribe" ->
      send_presence(To, From, "subscribe");
    "subscribed" ->
      send_presence(To, From, "subscribed"),
      send_presence(To, From, "");
    "unsubscribe" ->
      send_presence(To, From, "unsubscribed"),
      send_presence(To, From, "unsubscribe");
    "unsubscribed" ->
      send_presence(To, From, "unsubscribed");
    "" ->
      send_presence(To, From, "");
    "unavailable" ->
      ok;
    "probe" ->
      send_presence(To, From, "");
    _Other ->
      error_logger:info_msg("Other kind of presence~n~p", [Packet])
      %?INFO_MSG("Other kind of presence~n~p", [Packet])
  end,
  ok;

%route(From, #jid{luser = ?BOTNAME} = To, {xmlelement, "message", _, _} = Packet) ->
route(From, To, {xmlelement, "message", _, _} = Packet) ->
  case xml:get_subtag_cdata(Packet, "body") of
    "" ->
      ok;
    Body ->
  case xml:get_tag_attr_s("type", Packet) of

"error" ->
  error_logger:info_msg("Received error message~n~p -> ~p~n~p", [From, To, Packet]);
%?ERROR_MSG("Received error message~n~p -> ~p~n~p", [From, To, Packet]);
_ ->
echo(To, From, strip_bom(Body))
end
end,
ok.

%% HELPER FUNCTIONS

strip_bom([239,187,191|C]) -> C;
strip_bom(C) -> C.

send_presence(From, To, "") ->
  ejabberd_router:route(From, To, {xmlelement, "presence", [], []});

send_presence(From, To, TypeStr) ->
  ejabberd_router:route(From, To, {xmlelement, "presence", [{"type", TypeStr}], []}).

echo(From, To, Body) ->
  send_message(From, To, "chat", Body).

send_message(From, To, TypeStr, BodyStr) ->
  XmlBody = {xmlelement, "message",
    [{"type", TypeStr},
      {"from", jlib:jid_to_string(From)},
      {"to", jlib:jid_to_string(To)}],
    [{xmlelement, "body", [],
      [{xmlcdata, BodyStr}]}]},
  ejabberd_router:route(From, To, XmlBody).

Hi Steven
I'm stumbling upon the same problem with echo bots like you. I've tried to debug and get a working version on internet and I have even found your question on stackoverflow. Now with your code (the same above) I have a bot but I cannot send anything to it.
I have the ejabberd domain/host: chat.domain.local, I'm using a common xmpp client (psi) and after a service discovery I have added "echo.chat.domain.local" to my service Agent/Transport list in the xmpp client. I can send messages but I cannot see anything back.
I'm using ejabberd v16.02 (x64) on a CentOS 6.7 machine.
Here're the error messages I can see in my ejabberd.log

2016-04-21 17:53:02.327 [error] <0.6289.0>@ejabberd_router:route:77 {function_clause,[{mod_echobot,route,[{jid,<<"ben">>,<<"chat.domain.local">>,<<"MyCustomResourceID">>,<<"ben">>,<<"chat.domain.local">>,<<"MyCustomResourceID">>},{jid,<<>>,<<"echo.chat.domain.local">>,<<>>,<<>>,<<"echo.chat.domain.local">>,<<>>},{xmlel,<<"message">>,[{<<"xml:lang">>,<<"en">>},{<<"type">>,<<"chat">>},{<<"to">>,<<"echo.chat.domain.local">>},{<<"id">>,<<"aae0a">>}],[{xmlcdata,<<"\n">>},{xmlel,<<"body">>,[],[{xmlcdata,<<"test 123">>}]},{xmlcdata,<<"\n">>},{xmlel,<<"active">>,[{<<"xmlns">>,<<"http://jabber.org/protocol/chatstates">>}],[]},{xmlcdata,<<"\n">>},{xmlel,<<"nick">>,[{<<"xmlns">>,<<"http://jabber.org/protocol/nick">>}],[{xmlcdata,<<"Ben">>}]},{xmlcdata,<<"\n">>}]}],[{file,"src/mod_echobot.erl"},{line,105}]},{ejabberd_router,route,3,[{file,"src/ejabberd_router.erl"},{line,75}]},{ejabberd_c2s,check_privacy_route,5,[{file,"src/ejabberd_c2s.erl"},{line,2113}]},{ejabberd_c2s,session_established2,2,[{file,"src/ejabberd_c2s.erl"},{line,1278}]},{p1_fsm,handle_msg,10,[{file,"src/p1_fsm.erl"},{line,582}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,237}]}]}
when processing: {{jid,<<"ben">>,<<"chat.domain.local">>,<<"MyCustomResourceID">>,<<"ben">>,<<"chat.domain.local">>,<<"MyCustomResourceID">>},{jid,<<>>,<<"echo.chat.domain.local">>,<<>>,<<>>,<<"echo.chat.domain.local">>,<<>>},{xmlel,<<"message">>,[{<<"xml:lang">>,<<"en">>},{<<"type">>,<<"chat">>},{<<"to">>,<<"echo.chat.domain.local">>},{<<"id">>,<<"aae0a">>}],[{xmlcdata,<<"\n">>},{xmlel,<<"body">>,[],[{xmlcdata,<<"test 123">>}]},{xmlcdata,<<"\n">>},{xmlel,<<"active">>,[{<<"xmlns">>,<<"http://jabber.org/protocol/chatstates">>}],[]},{xmlcdata,<<"\n">>},{xmlel,<<"nick">>,[{<<"xmlns">>,<<"http://jabber.org/protocol/nick">>}],[{xmlcdata,<<"Ben">>}]},{xmlcdata,<<"\n">>}]}}

It seems there's a problem with the route() function but I cannot understand why, are you able to test it or can you tell me something more about it ? It's running with your own code (downloaded on 2016/04/21)

Cheers
Ben