diff --git a/metro.cabal b/metro.cabal
--- a/metro.cabal
+++ b/metro.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 24d5ce7bcac547eb3eeb276c1486b3d82bc04c04fc1805c000dd3d0b3f402547
+-- hash: 07882b5a43e7863f722e3718c4a967123818ae24bfb31cadfcfe24c420cb8799
 
 name:           metro
-version:        0.1.0.2
+version:        0.1.0.3
 synopsis:       A simple tcp and udp socket server framework
 description:    Please see the README on GitHub at <https://github.com/Lupino/metro#readme>
 category:       Network,Framework
diff --git a/src/Metro/Node.hs b/src/Metro/Node.hs
--- a/src/Metro/Node.hs
+++ b/src/Metro/Node.hs
@@ -91,7 +91,7 @@
     , sessionGen  :: IO k
     , nodeTimer   :: TVar Int64
     , nodeId      :: nid
-    , sessTimeout :: Int64
+    , sessTimeout :: TVar Int64
     , onNodeLeave :: TVar (Maybe (u -> IO ()))
     }
 
@@ -129,15 +129,15 @@
 
 initEnv :: MonadIO m => u -> nid -> IO k -> m (NodeEnv u nid k rpkt)
 initEnv uEnv nodeId sessionGen = do
-  nodeStatus <- newTVarIO True
+  nodeStatus  <- newTVarIO True
   nodeSession <- newTVarIO Nothing
   sessionList <- newIOHashMap
-  nodeTimer <- newTVarIO =<< getEpochTime
+  nodeTimer   <- newTVarIO =<< getEpochTime
   onNodeLeave <- newTVarIO Nothing
+  sessTimeout <- newTVarIO 300
   pure NodeEnv
     { nodeMode    = Multi
     , sessionMode = SingleAction
-    , sessTimeout = 300
     , ..
     }
 
@@ -152,7 +152,7 @@
 setSessionMode :: SessionMode -> NodeEnv u nid k rpkt -> NodeEnv u nid k rpkt
 setSessionMode mode nodeEnv = nodeEnv {sessionMode = mode}
 
-setDefaultSessionTimeout :: Int64 -> NodeEnv u nid k rpkt -> NodeEnv u nid k rpkt
+setDefaultSessionTimeout :: TVar Int64 -> NodeEnv u nid k rpkt -> NodeEnv u nid k rpkt
 setDefaultSessionTimeout t nodeEnv = nodeEnv { sessTimeout = t }
 
 initEnv1
@@ -185,7 +185,8 @@
 newSessionEnv :: (MonadIO m, Eq k, Hashable k) => Maybe Int64 -> k -> NodeT u nid k rpkt tp m (SessionEnv u nid k rpkt)
 newSessionEnv sTout sid = do
   NodeEnv{..} <- ask
-  sEnv <- S.newSessionEnv uEnv nodeId sid (fromMaybe sessTimeout sTout) []
+  dTout <- readTVarIO sessTimeout
+  sEnv <- S.newSessionEnv uEnv nodeId sid (fromMaybe dTout sTout) []
   case nodeMode of
     Single -> atomically $ do
       sess <- readTVar nodeSession
@@ -255,7 +256,8 @@
       runSessionT_ aEnv $ feed $ Just rpkt
     Nothing    -> do
       let sid = getPacketId rpkt
-      sEnv <- S.newSessionEnv uEnv nodeId sid sessTimeout [Just rpkt]
+      dTout <- readTVarIO sessTimeout
+      sEnv <- S.newSessionEnv uEnv nodeId sid dTout [Just rpkt]
       when (sessionMode == MultiAction) $
         case nodeMode of
           Single -> atomically $ writeTVar nodeSession $ Just sEnv
diff --git a/src/Metro/Server.hs b/src/Metro/Server.hs
--- a/src/Metro/Server.hs
+++ b/src/Metro/Server.hs
@@ -64,8 +64,8 @@
     , nodeEnvList  :: IOHashMap nid (NodeEnv1 u nid k rpkt tp)
     , prepare      :: SID serv -> ConnEnv tp -> IO (Maybe (nid, u))
     , gen          :: IO k
-    , keepalive    :: Int64
-    , defSessTout  :: Int64
+    , keepalive    :: TVar Int64 -- client keepalive seconds
+    , defSessTout  :: TVar Int64 -- session timeout seconds
     , nodeMode     :: NodeMode
     , sessionMode  :: SessionMode
     , serveName    :: String
@@ -106,12 +106,12 @@
   serveState  <- newTVarIO True
   nodeEnvList <- newIOHashMap
   onNodeLeave <- newTVarIO Nothing
+  keepalive   <- newTVarIO 0
+  defSessTout <- newTVarIO 300
   pure ServerEnv
     { nodeMode    = Multi
     , sessionMode = SingleAction
     , serveName   = "Metro"
-    , keepalive   = 0
-    , defSessTout = 300
     , ..
     }
 
@@ -128,16 +128,17 @@
 setServerName n sEnv = sEnv {serveName = n}
 
 setKeepalive
-  :: Int64 -> ServerEnv serv u nid k rpkt tp -> ServerEnv serv u nid k rpkt tp
-setKeepalive k sEnv = sEnv {keepalive = k}
+  :: MonadIO m => ServerEnv serv u nid k rpkt tp -> Int -> m ()
+setKeepalive sEnv =
+  atomically . writeTVar (keepalive sEnv) . fromIntegral
 
 setDefaultSessionTimeout
-  :: Int64 -> ServerEnv serv u nid k rpkt tp -> ServerEnv serv u nid k rpkt tp
-setDefaultSessionTimeout t sEnv = sEnv {defSessTout = t}
+  :: MonadIO m => ServerEnv serv u nid k rpkt tp -> Int -> m ()
+setDefaultSessionTimeout sEnv =
+  atomically . writeTVar (defSessTout sEnv) . fromIntegral
 
 setOnNodeLeave :: MonadIO m => ServerEnv serv u nid k rpkt tp -> (nid -> u -> IO ()) -> m ()
-setOnNodeLeave sEnv =
-  atomically . writeTVar (onNodeLeave sEnv) . Just
+setOnNodeLeave sEnv = atomically . writeTVar (onNodeLeave sEnv) . Just
 
 serveForever
   :: (MonadUnliftIO m, Transport tp, Show nid, Eq nid, Hashable nid, Eq k, Hashable k, GetPacketId k rpkt, RecvPacket rpkt, Servable serv)
@@ -249,7 +250,7 @@
   -> SessionT u nid k rpkt tp m ()
   -> m ()
 startServer_ sEnv preprocess sess = do
-  when (keepalive sEnv > 0) $ runCheckNodeState (keepalive sEnv) (nodeEnvList sEnv)
+  runCheckNodeState (keepalive sEnv) (nodeEnvList sEnv)
   runServerT sEnv $ serveForever preprocess sess
   liftIO $ servClose $ serveServ sEnv
 
@@ -261,17 +262,20 @@
 
 runCheckNodeState
   :: (MonadUnliftIO m, Eq nid, Hashable nid, Transport tp)
-  => Int64 -> IOHashMap nid (NodeEnv1 u nid k rpkt tp) -> m ()
+  => TVar Int64 -> IOHashMap nid (NodeEnv1 u nid k rpkt tp) -> m ()
 runCheckNodeState alive envList = void . async . forever $ do
-  threadDelay $ fromIntegral alive * 1000 * 1000
-  mapM_ (checkAlive envList) =<< HM.elems envList
+  t <- readTVarIO alive
+  when (t > 0) $ do
+    threadDelay $ fromIntegral t * 1000 * 1000
+    mapM_ (checkAlive envList) =<< HM.elems envList
 
   where checkAlive
           :: (MonadUnliftIO m, Eq nid, Hashable nid, Transport tp)
           => IOHashMap nid (NodeEnv1 u nid k rpkt tp)
           -> NodeEnv1 u nid k rpkt tp -> m ()
         checkAlive ref env1 = runNodeT1 env1 $ do
-              expiredAt <- (alive +) <$> getTimer
+              t <- readTVarIO alive
+              expiredAt <- (t +) <$> getTimer
               now <- getEpochTime
               when (now > expiredAt) $ do
                 nid <- getNodeId