diff --git a/src/main/jni/Android.mk b/src/main/jni/Android.mk
index 3907cf7a..7441563a 100755
--- a/src/main/jni/Android.mk
+++ b/src/main/jni/Android.mk
@@ -160,6 +160,25 @@ LOCAL_SRC_FILES := $(addprefix shadowsocks-libev/libcork/,$(CORK_SOURCE))
 
 include $(BUILD_STATIC_LIBRARY)
 
+########################################################
+## libudns
+########################################################
+
+include $(CLEAR_VARS)
+
+UDNS_SOURCES := udns_dn.c udns_dntosp.c udns_parse.c udns_resolver.c udns_init.c \
+	udns_misc.c udns_XtoX.c \
+	udns_rr_a.c udns_rr_ptr.c udns_rr_mx.c udns_rr_txt.c udns_bl.c \
+	udns_rr_srv.c udns_rr_naptr.c udns_codes.c udns_jran.c
+
+LOCAL_MODULE := libudns
+LOCAL_CFLAGS += -O2 -I$(LOCAL_PATH)/shadowsocks-libev/libudns \
+				-DHAVE_DECL_INET_NTOP
+
+LOCAL_SRC_FILES := $(addprefix shadowsocks-libev/libudns/,$(UDNS_SOURCES))
+
+include $(BUILD_STATIC_LIBRARY)
+
 ########################################################
 ## libev 
 ########################################################
@@ -223,12 +242,13 @@ LOCAL_CFLAGS    := -Wall -O2 -fno-strict-aliasing -DUDPRELAY_LOCAL \
 					-DUSE_CRYPTO_OPENSSL -DANDROID -DHAVE_CONFIG_H \
 					-I$(LOCAL_PATH)/libev/ \
 					-I$(LOCAL_PATH)/openssl/include  \
+					-I$(LOCAL_PATH)/shadowsocks-libev/libudns \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libcork/include \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libsodium/src/libsodium/include \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libsodium/src/libsodium/include/sodium \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libipset/include
 
-LOCAL_STATIC_LIBRARIES := libev libcrypto libipset libcork libsodium
+LOCAL_STATIC_LIBRARIES := libev libcrypto libipset libcork libudns libsodium
 
 LOCAL_LDLIBS := -llog
 
@@ -247,11 +267,13 @@ LOCAL_SRC_FILES := $(addprefix shadowsocks-libev/src/, $(SHADOWSOCKS_SOURCES))
 LOCAL_CFLAGS    := -Wall -O2 -fno-strict-aliasing -DUDPRELAY_LOCAL -DUDPRELAY_TUNNEL \
 					-DUSE_CRYPTO_OPENSSL -DANDROID -DHAVE_CONFIG_H -DSSTUNNEL_JNI \
 					-I$(LOCAL_PATH)/libev/ \
+					-I$(LOCAL_PATH)/shadowsocks-libev/libudns \
+					-I$(LOCAL_PATH)/shadowsocks-libev/libcork/include \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libsodium/src/libsodium/include \
 					-I$(LOCAL_PATH)/shadowsocks-libev/libsodium/src/libsodium/include/sodium \
 					-I$(LOCAL_PATH)/openssl/include 
 
-LOCAL_STATIC_LIBRARIES := libev libcrypto libsodium
+LOCAL_STATIC_LIBRARIES := libev libcrypto libsodium libcork libudns
 
 LOCAL_LDLIBS := -llog
 
diff --git a/src/main/jni/shadowsocks-libev b/src/main/jni/shadowsocks-libev
index 2a15e971..9cdc3dc7 160000
--- a/src/main/jni/shadowsocks-libev
+++ b/src/main/jni/shadowsocks-libev
@@ -1 +1 @@
-Subproject commit 2a15e971969a1e068fc93b1c32d27de4814d1de8
+Subproject commit 9cdc3dc7ef8e7a87169755a6b4287a5394745dd1
diff --git a/src/main/scala/com/github/shadowsocks/ShadowsocksNatService.scala b/src/main/scala/com/github/shadowsocks/ShadowsocksNatService.scala
index bdef7894..3bbc96a5 100644
--- a/src/main/scala/com/github/shadowsocks/ShadowsocksNatService.scala
+++ b/src/main/scala/com/github/shadowsocks/ShadowsocksNatService.scala
@@ -513,31 +513,33 @@ class ShadowsocksNatService extends Service with BaseService {
     }
     registerReceiver(closeReceiver, filter)
 
-    val screenFilter = new IntentFilter()
-    screenFilter.addAction(Intent.ACTION_SCREEN_ON)
-    screenFilter.addAction(Intent.ACTION_SCREEN_OFF)
-    screenFilter.addAction(Intent.ACTION_USER_PRESENT)
-    lockReceiver = new BroadcastReceiver() {
-      def onReceive(context: Context, intent: Intent) {
-        if (getState == State.CONNECTED) {
-          val action = intent.getAction
-          if (action == Intent.ACTION_SCREEN_OFF) {
-            notifyForegroundAlert(getString(R.string.forward_success),
-              getString(R.string.service_running).formatLocal(Locale.ENGLISH, config.profileName), false)
-          } else if (action == Intent.ACTION_SCREEN_ON) {
-            val keyGuard = getSystemService(Context.KEYGUARD_SERVICE).asInstanceOf[KeyguardManager]
-            if (!keyGuard.inKeyguardRestrictedInputMode) {
+    if (Utils.isLollipopOrAbove) {
+      val screenFilter = new IntentFilter()
+      screenFilter.addAction(Intent.ACTION_SCREEN_ON)
+      screenFilter.addAction(Intent.ACTION_SCREEN_OFF)
+      screenFilter.addAction(Intent.ACTION_USER_PRESENT)
+      lockReceiver = new BroadcastReceiver() {
+        def onReceive(context: Context, intent: Intent) {
+          if (getState == State.CONNECTED) {
+            val action = intent.getAction
+            if (action == Intent.ACTION_SCREEN_OFF) {
+              notifyForegroundAlert(getString(R.string.forward_success),
+                getString(R.string.service_running).formatLocal(Locale.ENGLISH, config.profileName), false)
+            } else if (action == Intent.ACTION_SCREEN_ON) {
+              val keyGuard = getSystemService(Context.KEYGUARD_SERVICE).asInstanceOf[KeyguardManager]
+              if (!keyGuard.inKeyguardRestrictedInputMode) {
+                notifyForegroundAlert(getString(R.string.forward_success),
+                  getString(R.string.service_running).formatLocal(Locale.ENGLISH, config.profileName), true)
+            }
+            } else if (action == Intent.ACTION_USER_PRESENT) {
               notifyForegroundAlert(getString(R.string.forward_success),
                 getString(R.string.service_running).formatLocal(Locale.ENGLISH, config.profileName), true)
             }
-          } else if (action == Intent.ACTION_USER_PRESENT) {
-            notifyForegroundAlert(getString(R.string.forward_success),
-              getString(R.string.service_running).formatLocal(Locale.ENGLISH, config.profileName), true)
+            }
           }
         }
-      }
+        registerReceiver(lockReceiver, screenFilter)
     }
-    registerReceiver(lockReceiver, screenFilter)
 
     // send event
     application.tracker.send(new HitBuilders.EventBuilder()
@@ -606,9 +608,12 @@ class ShadowsocksNatService extends Service with BaseService {
       unregisterReceiver(closeReceiver)
       closeReceiver = null
     }
-    if (lockReceiver != null) {
-      unregisterReceiver(lockReceiver)
-      lockReceiver = null
+
+    if (Utils.isLollipopOrAbove) {
+      if (lockReceiver != null) {
+        unregisterReceiver(lockReceiver)
+        lockReceiver = null
+      }
     }
 
     // send event