diff --git a/include/emqtt.hrl b/include/emqtt.hrl
index f4ba9e6d..1fd4a764 100644
--- a/include/emqtt.hrl
+++ b/include/emqtt.hrl
@@ -17,14 +17,6 @@
 -ifndef(EMQTT_HRL).
 -define(EMQTT_HRL, true).
 
-%%--------------------------------------------------------------------
-%% MQTT SockOpts
-%%--------------------------------------------------------------------
-
--define(MQTT_SOCKOPTS, [binary, {packet, raw},
-                                {backlog, 512},
-                                {nodelay, true}]).
-
 %%--------------------------------------------------------------------
 %% MQTT Protocol Version and Names
 %%--------------------------------------------------------------------
diff --git a/rebar.config b/rebar.config
index e5d22823..762a976e 100644
--- a/rebar.config
+++ b/rebar.config
@@ -7,10 +7,10 @@
             warn_obsolete_guard
            ]}.
 
-{deps, [{cowlib, "2.6.0"},
-		{gun, "1.3.0"},
+{deps, [{cowlib, "2.8.0"},
+        {gun, {git, "https://github.com/emqx/gun", {tag, "1.3.4"}}},
         {getopt, "1.0.1"},
-        {esasl, {git, "https://github.com/emqx/esasl", {tag, "master"}}}
+        esasl, {git, "https://github.com/emqx/esasl", {tag, "master"}}}
        ]}.
 
 {escript_name, emqtt_cli}.
diff --git a/src/emqtt.appup.src b/src/emqtt.appup.src
new file mode 100644
index 00000000..c7e63aae
--- /dev/null
+++ b/src/emqtt.appup.src
@@ -0,0 +1,13 @@
+%% -*-: erlang -*-
+{"1.2.3",
+  [{<<"1.2.*">>, [
+     {load_module, emqtt_sock, brutal_purge, soft_purge, []},
+     {load_module, emqtt, brutal_purge, soft_purge, []}
+    ]}
+  ],
+  [{<<"1.2.*">>, [
+     {load_module, emqtt_sock, brutal_purge, soft_purge, []},
+     {load_module, emqtt, brutal_purge, soft_purge, []}
+    ]}
+  ]
+}.
diff --git a/src/emqtt.erl b/src/emqtt.erl
index 13c3b32e..fd33fd34 100644
--- a/src/emqtt.erl
+++ b/src/emqtt.erl
@@ -102,9 +102,12 @@
 %% Message handler is a set of callbacks defined to handle MQTT messages
 %% as well as the disconnect event.
 -define(NO_MSG_HDLR, undefined).
--type(msg_handler() :: #{puback := fun((_) -> any()),
-                         publish := fun((emqx_types:message()) -> any()),
-                         disconnected := fun(({reason_code(), _Properties :: term()}) -> any())
+
+-type(mfas() :: {module(), atom(), list()} | {function(), list()}).
+
+-type(msg_handler() :: #{puback := fun((_) -> any()) | mfas(),
+                         publish := fun((emqx_types:message()) -> any()) | mfas(),
+                         disconnected := fun(({reason_code(), _Properties :: term()}) -> any()) | mfas()
                         }).
 
 -type(option() :: {name, atom()}
@@ -1067,6 +1070,8 @@ connected(info, {timeout, TRef, keepalive},
         true ->
             case send(?PACKET(?PINGREQ), State) of
                 {ok, NewState} ->
+                    {ok, [{send_oct, Val}]} = ConnMod:getstat(Sock, [send_oct]),
+                    put(send_oct, Val),
                     {keep_state, ensure_keepalive_timer(NewState), [hibernate]};
                 Error -> {stop, Error}
             end;
@@ -1359,9 +1364,22 @@ eval_msg_handler(#state{msg_handler = ?NO_MSG_HDLR,
     ok;
 eval_msg_handler(#state{msg_handler = Handler}, Kind, Msg) ->
     F = maps:get(Kind, Handler),
-    _ = F(Msg),
+    _ = apply_handler_function(F, Msg),
     ok.
 
+apply_handler_function(F, Msg)
+  when is_function(F) ->
+    erlang:apply(F, [Msg]);
+apply_handler_function({F, A}, Msg)
+  when is_function(F),
+       is_list(A) ->
+    erlang:apply(F, [Msg] ++ A);
+apply_handler_function({M, F, A}, Msg)
+  when is_atom(M),
+       is_atom(F),
+       is_list(A) ->
+    erlang:apply(M, F, [Msg] ++ A).
+
 packet_to_msg(#mqtt_packet{header   = #mqtt_packet_header{type   = ?PUBLISH,
                                                           dup    = Dup,
                                                           qos    = QoS,
diff --git a/src/emqtt_sock.erl b/src/emqtt_sock.erl
index 8de3c35b..f5ea9062 100644
--- a/src/emqtt_sock.erl
+++ b/src/emqtt_sock.erl
@@ -38,7 +38,7 @@
 -export_type([socket/0, option/0]).
 
 -define(DEFAULT_TCP_OPTIONS, [binary, {packet, raw}, {active, false},
-                              {nodelay, true}, {reuseaddr, true}]).
+                              {nodelay, true}]).
 
 -spec(connect(inet:ip_address() | inet:hostname(),
               inet:port_number(), [option()], timeout())