diff --git a/src/emqtt_client.erl b/src/emqtt_client.erl
index d76617f10..ea2eb9772 100644
--- a/src/emqtt_client.erl
+++ b/src/emqtt_client.erl
@@ -123,7 +123,8 @@ handle_info(keep_alive_timeout, #state{keep_alive=KeepAlive}=State) ->
 handle_info(Info, State) ->
 	{stop, {badinfo, Info}, State}.
 
-terminate(_Reason, #state{keep_alive=KeepAlive}) ->
+terminate(_Reason, #state{client_id=ClientId, keep_alive=KeepAlive}) ->
+    ok = emqtt_registry:unregister(ClientId),
 	emqtt_keep_alive:cancel(KeepAlive),
 	ok.
 
@@ -201,6 +202,7 @@ process_request(?CONNECT,
                         ?ERROR_MSG("MQTT login failed - no credentials"),
                         {?CONNACK_CREDENTIALS, State};
                     true ->
+						ok = emqtt_registry:register(ClientId, self()),
 						KeepAlive = emqtt_keep_alive:new(AlivePeriod*1500, keep_alive_timeout),
 						{?CONNACK_ACCEPT,
 						 State #state{ will_msg   = make_will_msg(Var),
@@ -355,6 +357,7 @@ control_throttle(State = #state{ connection_state = Flow,
     end.
 
 stop(Reason, State ) ->
+
     {stop, Reason, State}.
 
 valid_client_id(ClientId) ->
diff --git a/src/emqtt_registry.erl b/src/emqtt_registry.erl
new file mode 100644
index 000000000..7f437234f
--- /dev/null
+++ b/src/emqtt_registry.erl
@@ -0,0 +1,83 @@
+-module(emqtt_registry).
+
+-include("emqtt.hrl").
+
+-export([start_link/0, 
+		size/0,
+		register/2,
+		unregister/1]).
+
+-behaviour(gen_server).
+
+-export([init/1,
+		 handle_call/3,
+		 handle_cast/2,
+		 handle_info/2,
+         terminate/2,
+		 code_change/3]).
+
+-record(state, {}).
+
+-define(SERVER, ?MODULE).
+
+%%----------------------------------------------------------------------------
+
+start_link() ->
+    gen_server2:start_link({local, ?SERVER}, ?MODULE, [], []).
+
+size() ->
+	ets:info(client, size).
+
+register(ClientId, Pid) ->
+    gen_server2:cast(?SERVER, {register, ClientId, Pid}).
+
+unregister(ClientId) ->
+    gen_server2:cast(?SERVER, {unregister, ClientId}).
+
+%%----------------------------------------------------------------------------
+
+init([]) ->
+	ets:new(client, [set, protected, named_table]),
+	?INFO("~p is started.", [?MODULE]),
+    {ok, #state{}}. % clientid -> {pid, monitor}
+
+%%--------------------------------------------------------------------------
+handle_call(Req, _From, State) ->
+    {stop, {badreq, Req}, State}.
+
+handle_cast({register, ClientId, Pid}, State) ->
+	?INFO("register ~p ~p", [ClientId, Pid]),
+	case ets:lookup(client, ClientId) of
+	[{_, {OldPid, MRef}}] ->
+		catch gen_server2:call(OldPid, duplicate_id),
+		erlang:demonitor(MRef);
+	[] ->
+		ignore
+	end,
+	ets:insert(client, {ClientId, {Pid, erlang:monitor(process, Pid)}}),
+    {noreply, State};
+
+handle_cast({unregister, ClientId}, State) ->
+	?INFO("unregister ~p", [ClientId]),
+	case ets:lookup(client, ClientId) of
+	[{_, {_Pid, MRef}}] ->
+		erlang:demonitor(MRef),
+		ets:delete(client, ClientId);
+	[] ->
+		ignore
+	end,
+	{noreply, State};
+
+handle_cast(Msg, State) ->
+    {stop, {badmsg, Msg}, State}.
+
+handle_info({'DOWN', MRef, process, DownPid, _Reason}, State) ->
+	ets:match_delete(client, {'_', {DownPid, MRef}}),
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    ok.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
diff --git a/src/emqtt_sup.erl b/src/emqtt_sup.erl
index 59ec7fdd7..5bdb3699a 100644
--- a/src/emqtt_sup.erl
+++ b/src/emqtt_sup.erl
@@ -29,6 +29,7 @@ init([Listeners]) ->
 		?CHILD(emqtt_auth, worker),
 		?CHILD(emqtt_retained, worker),
 		?CHILD(emqtt_router, worker),
+		?CHILD(emqtt_registry, worker),
 		?CHILD(emqtt_client_sup, supervisor)
 		| listener_children(Listeners) ]}
 	}.