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diff --git a/lib/diameter/examples/relay_cb.erl b/lib/diameter/examples/relay_cb.erl
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+++ b/lib/diameter/examples/relay_cb.erl
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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(relay_cb).
+
+-include_lib("diameter/include/diameter.hrl").
+-include_lib("diameter/src/app/diameter_gen_base_rfc3588.hrl").
+
+%% diameter callbacks
+-export([peer_up/3,
+         peer_down/3,
+         pick_peer/5,
+         prepare_request/4,
+         prepare_retransmit/4,
+         handle_answer/5,
+         handle_error/5,
+         handle_request/3]).
+
+peer_up(_SvcName, {PeerRef, _}, State) ->
+    io:format("up: ~p~n", [PeerRef]),
+    State.
+
+peer_down(_SvcName, {PeerRef, _}, State) ->
+    io:format("down: ~p~n", [PeerRef]),
+    State.
+
+%% Returning 'relay' from handle_request causes diameter to resend the
+%% incoming request, which leads to pick_peer and prepare_request
+%% callbacks as if sending explicitly. The 'extra' argument is
+%% appended to the argument list for callbacks following from
+%% resending of the request.
+
+handle_request(_Pkt, _SvcName, _Peer) ->
+    {relay, [{timeout, 1000}, {extra, [relayed]}]}.
+
+%% diameter will filter the sender in the Peers list.
+pick_peer([Peer | _], _, _SvcName, _State, relayed) ->
+    {ok, Peer}.
+
+prepare_request(Pkt, _SvcName, _Peer, relayed) ->
+    {send, Pkt}.
+
+prepare_retransmit(Pkt, _SvcName, _Peer, relayed) ->
+    {send, Pkt}.
+
+%% diameter expects handle_answer to return the diameter_packet record
+%% containing the answer when called for a relayed request.
+
+handle_answer(Pkt, _Request, _SvcName, _Peer, relayed) ->
+    Pkt.
+
+handle_error(Reason, _Request, _SvcName, _Peer, relayed) ->
+    {error, Reason}.