diff --git a/apps/emqtt/src/emqtt_protocol.erl b/apps/emqtt/src/emqtt_protocol.erl
index 6900924bb..0e2a22354 100644
--- a/apps/emqtt/src/emqtt_protocol.erl
+++ b/apps/emqtt/src/emqtt_protocol.erl
@@ -138,10 +138,8 @@ handle_packet(?CONNECT, Packet = #mqtt_packet {
     send_packet( #mqtt_packet {
                     header = #mqtt_packet_header { type = ?CONNACK }, 
                     variable = #mqtt_packet_connack{ return_code = ReturnCode1 }}, State1 ),
-    %%
+    %%Starting session
     {ok, Session} = emqtt_session:start({CleanSess, ClientId, self()}),
-    emqtt_session:resume(Session),
-    %%TODO: Resume session
     {ok, State1#proto_state { session = Session }};
 
 handle_packet(?PUBLISH, Packet = #mqtt_packet {
diff --git a/apps/emqtt/src/emqtt_session.erl b/apps/emqtt/src/emqtt_session.erl
index ae6271098..059a70e34 100644
--- a/apps/emqtt/src/emqtt_session.erl
+++ b/apps/emqtt/src/emqtt_session.erl
@@ -31,6 +31,8 @@
 %% ------------------------------------------------------------------
 -export([start/1, resume/1, publish/2, puback/2]).
 
+%%start gen_server
+-export([start_link/3]).
 %% ------------------------------------------------------------------
 %% gen_server Function Exports
 %% ------------------------------------------------------------------
@@ -45,22 +47,30 @@
         subscriptions = [],
         messages = [], %% do not receive rel
 		awaiting_ack,
-        awaiting_rel }).
+        awaiting_rel,
+        expires,
+        max_queue }).
 
 %% ------------------------------------------------------------------
-%% API Function Definitions
+%% Start Session
 %% ------------------------------------------------------------------
-start({true = CleanSess, ClientId, ClientPid}) ->
-    %%destroy old session
-    %%TODO: emqtt_sm:destory_session(ClientId),
+start({true = CleanSess, ClientId, _ClientPid}) ->
+    %%Destroy old session if CleanSess is true before.
+    ok = emqtt_sm:destory_session(ClientId),
     {ok, initial_state(ClientId)};
 
 start({false = CleanSess, ClientId, ClientPid}) ->
-    %%TODO: emqtt_sm:start_session({ClientId, ClientPid})
-    gen_server:start_link(?MODULE, [ClientId, ClientPid], []).
+    {ok, SessPid} = emqtt_sm:start_session(ClientId, ClientPid),
+    {ok, SessPid}.
 
-resume(#session_state {}) -> 'TODO';
-resume(SessPid) when is_pid(SessPid) -> 'TODO'.
+%% ------------------------------------------------------------------
+%% Session API
+%% ------------------------------------------------------------------
+resume(SessState = #session_state{}, _ClientPid) -> 
+    SessState;
+resume(SessPid, ClientPid) when is_pid(SessPid) -> 
+    gen_server:cast(SessPid, {resume, ClientPid}),
+    SessPid.
 
 publish(_, {?QOS_0, Message}) ->
     emqtt_router:route(Message);
@@ -113,10 +123,16 @@ initial_state(ClientId, ClientPid) ->
 %% gen_server Function Definitions
 %% ------------------------------------------------------------------
 
-init([ClientId, ClientPid]) ->
+start_link(SessOpts, ClientId, ClientPid) ->
+    gen_server:start_link(?MODULE, [SessOpts, ClientId, ClientPid], []).
+
+init([SessOpts, ClientId, ClientPid]) ->
     process_flag(trap_exit, true),
+    %%TODO: OK?
+    true = link(ClientPid),
     State = initial_state(ClientId, ClientPid),
-    {ok, State}.
+    {ok, State#state{ expires = proplists:get_value(expires, SessOpts, 24) * 3600, 
+                      max_queue = proplists:get_value(max_queue, SessOpts, 1000) } }.
 
 handle_call(_Request, _From, State) ->
     {reply, ok, State}.
diff --git a/apps/emqtt/src/emqtt_session_sup.erl b/apps/emqtt/src/emqtt_session_sup.erl
new file mode 100644
index 000000000..d4a118bbf
--- /dev/null
+++ b/apps/emqtt/src/emqtt_session_sup.erl
@@ -0,0 +1,57 @@
+%%-----------------------------------------------------------------------------
+%% Copyright (c) 2012-2015, Feng Lee <feng@emqtt.io>
+%% 
+%% Permission is hereby granted, free of charge, to any person obtaining a copy
+%% of this software and associated documentation files (the "Software"), to deal
+%% in the Software without restriction, including without limitation the rights
+%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+%% copies of the Software, and to permit persons to whom the Software is
+%% furnished to do so, subject to the following conditions:
+%% 
+%% The above copyright notice and this permission notice shall be included in all
+%% copies or substantial portions of the Software.
+%% 
+%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+%% SOFTWARE.
+%%------------------------------------------------------------------------------
+
+-module(emqtt_session_sup).
+
+-author('feng@emqtt.io').
+
+-behavior(supervisor).
+
+-export([start_link/0, start_session/2]).
+
+-export([init/1]).
+
+%%----------------------------------------------------------------------------
+
+-ifdef(use_specs).
+
+-spec(start_link/1 :: (list(tuple())) -> {ok, pid()}).
+
+-spec(start_session/2 :: (binary(), pid()) -> {ok, pid()}).
+
+-endif.
+
+%%----------------------------------------------------------------------------
+
+start_link(SessOpts) ->
+    supervisor:start_link({local, ?MODULE}, ?MODULE, [SessOpts]).
+
+start_session(ClientId, ClientPid) ->
+    supervisor:start_child(?MODULE, [ClientId, ClientPid]).
+
+init([SessOpts]) ->
+    {ok, {{simple_one_for_one, 0, 1},
+          [{session, {emqtt_session, start_link, [SessOpts]},
+              transient, 10000, worker, [emqtt_session]}]}}.
+
+
+
diff --git a/apps/emqtt/src/emqtt_sm.erl b/apps/emqtt/src/emqtt_sm.erl
index 791d60ad7..7714034ef 100644
--- a/apps/emqtt/src/emqtt_sm.erl
+++ b/apps/emqtt/src/emqtt_sm.erl
@@ -47,13 +47,15 @@
 
 -define(SERVER, ?MODULE).
 
+-define(TABLE, emqtt_session).
+
 %% ------------------------------------------------------------------
 %% API Function Exports
 %% ------------------------------------------------------------------
 
--export([start_link/1]).
+-export([start_link/0]).
 
--export([lookup/1, register/2, resume/2, destroy/1]).
+-export([lookup_session/1, start_session/2, destroy_session/1]).
 
 %% ------------------------------------------------------------------
 %% gen_server Function Exports
@@ -62,34 +64,82 @@
 -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
          terminate/2, code_change/3]).
 
--record(state, { expires = 24, %hours 
-                 max_queue = 1000 }).
 
+%%----------------------------------------------------------------------------
+
+-ifdef(use_specs).
+
+-spec(start_link/0 :: () -> {ok, pid()}).
+
+-spec(lookup_session/1 :: (binary()) -> pid() | undefined).
+
+-spec(start_session/2 :: (binary(), pid()) -> {ok, pid()} | {error, any()}).
+
+-spec(destroy_session/1 :: (binary()) -> ok).
+
+-endif.
+
+%%----------------------------------------------------------------------------
+
+-record(state, {}).
 
 %% ------------------------------------------------------------------
 %% API Function Definitions
 %% ------------------------------------------------------------------
 
-start_link(SessOpts) ->
-    gen_server:start_link({local, ?SERVER}, ?MODULE, [SessOpts], []).
 
-lookup(ClientId) -> ok.
+start_link() ->
+    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
 
-register(ClientId, Pid) -> ok.
+lookup_session(ClientId) ->
+    case ets:lookup(?TABLE, ClientId) of
+        [{_, SessPid, _}] ->  SessPid;
+        [] -> undefined
+    end.
 
-resume(ClientId, Pid) -> ok.
+start_session(ClientId, ClientPid) ->
+    gen_server:call(?SERVER, {start_session, ClientId, ClientPid}).
 
-destroy(ClientId) -> ok.
+destory_session(ClientId) ->
+    gen_server:call(?SERVER, {destory_session, ClientId}).
 
 %% ------------------------------------------------------------------
 %% gen_server Function Definitions
 %% ------------------------------------------------------------------
 
-init(SessOpts) ->
-    State = #state{ expires = proplists:get_value(expires, SessOpts, 24) * 3600, 
-                    max_queue = proplists:get_value(max_queue, SessOpts, 1000) },
+init() ->
+    process_flag(trap_exit, true),
+    ets:new(?TABLE, [set, protected, named_table]),
     {ok, State}.
 
+handle_call({start_session, ClientId, ClientPid}, _From, State) ->
+    Reply =
+    case ets:lookup(?TABLE, ClientId) of
+        [{_, SessPid, MRef}] ->
+            emqtt_session:resume(SessPid, ClientPid), 
+            {ok, SessPid};
+        [] ->
+            case emqtt_session_sup:start_session(ClientId, ClientPid) of
+            {ok, SessPid} -> 
+                MRef = erlang:monitor(process, SessPid),
+                ets:insert(?TABLE, {ClientId, SessPid, MRef}),
+                {ok, SessPid};
+            {error, Error} ->
+                {error, Error}
+            end
+    end,
+    {reply, Reply, State};
+
+handle_call({destory_session, ClientId}, _From, State) ->
+    case ets:lookup(?TABLE, ClientId) of
+        [{_, SessPid, MRef}] ->
+            erlang:demonitor(MRef),
+            emqtt_session:destory(SessPid),
+            ets:delete(?TABLE, ClientId);
+        [] ->
+            ignore
+    end,
+    {reply, ok, State};
 
 handle_call(_Request, _From, State) ->
     {reply, ok, State}.
@@ -97,6 +147,10 @@ handle_call(_Request, _From, State) ->
 handle_cast(_Msg, State) ->
     {noreply, State}.
 
+handle_info({'DOWN', MRef, process, DownPid, _Reason}, State) ->
+	ets:match_delete(emqtt_client, {{'_', DownPid, MRef}}),
+    {noreply, State};
+
 handle_info(_Info, State) ->
     {noreply, State}.
 
@@ -106,3 +160,4 @@ terminate(_Reason, _State) ->
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
 
+