diff --git a/app/src/main/java/com/lipisoft/toyshark/PacketManager.kt b/app/src/main/java/com/lipisoft/toyshark/PacketManager.kt
index 3d22ff2..01014d0 100644
--- a/app/src/main/java/com/lipisoft/toyshark/PacketManager.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/PacketManager.kt
@@ -29,10 +29,6 @@ enum class PacketManager {
         return list.add(packet)
     }
 
-    fun getList(): List<Packet> {
-        return list
-    }
-
     fun setAdapter(adapter: PacketListAdapter) {
         this.adapter = adapter
     }
diff --git a/app/src/main/java/com/lipisoft/toyshark/ToySharkVPNService.kt b/app/src/main/java/com/lipisoft/toyshark/ToySharkVPNService.kt
index 4de7d0d..2647437 100644
--- a/app/src/main/java/com/lipisoft/toyshark/ToySharkVPNService.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/ToySharkVPNService.kt
@@ -342,6 +342,7 @@ class ToySharkVPNService : VpnService(), Handler.Callback, Runnable, IProtectSoc
         }
 
         Log.i(TAG, "startVpnService => create builder")
+
         // Configure a builder while parsing the parameters.
         val builder = Builder()
                 .addAddress("10.120.0.1", 32)
@@ -350,12 +351,12 @@ class ToySharkVPNService : VpnService(), Handler.Callback, Runnable, IProtectSoc
 
         fileDescriptor = builder.establish()
 
-        if (fileDescriptor != null) {
+        return if (fileDescriptor != null) {
             Log.i(TAG, "VPN Established:interface = " + fileDescriptor!!.fileDescriptor.toString())
-            return true
+            true
         } else {
             Log.d(TAG, "fileDescriptor is null")
-            return false
+            false
         }
     }
 
diff --git a/app/src/main/java/com/lipisoft/toyshark/network/ip/IPPacketFactory.kt b/app/src/main/java/com/lipisoft/toyshark/network/ip/IPPacketFactory.kt
index 6ce156e..cbb6775 100755
--- a/app/src/main/java/com/lipisoft/toyshark/network/ip/IPPacketFactory.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/network/ip/IPPacketFactory.kt
@@ -45,7 +45,7 @@ object IPPacketFactory {
                 iPv4Header.totalLength,
                 iPv4Header.identification,
                 iPv4Header.isMayFragment,
-                iPv4Header.isLastFragment,
+                iPv4Header.lastFragment,
                 iPv4Header.fragmentOffset,
                 iPv4Header.timeToLive,
                 iPv4Header.protocol,
diff --git a/app/src/main/java/com/lipisoft/toyshark/network/ip/IPv4Header.kt b/app/src/main/java/com/lipisoft/toyshark/network/ip/IPv4Header.kt
index 0040cab..2433aab 100755
--- a/app/src/main/java/com/lipisoft/toyshark/network/ip/IPv4Header.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/network/ip/IPv4Header.kt
@@ -54,7 +54,7 @@ class IPv4Header(
         var totalLength: Int,
         var identification: Int,
         private var mayFragment: Boolean,
-        val isLastFragment: Boolean,
+        val lastFragment: Boolean,
         val fragmentOffset: Short,
         val timeToLive: Byte,
         val protocol: Byte,
@@ -68,7 +68,7 @@ class IPv4Header(
         if (mayFragment)
             this.flag = this.flag or 0x40
 
-        if (isLastFragment)
+        if (lastFragment)
             this.flag = this.flag or 0x20
     }
 
diff --git a/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataReaderWorker.kt b/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataReaderWorker.kt
index 7051023..737d50e 100755
--- a/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataReaderWorker.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataReaderWorker.kt
@@ -30,6 +30,10 @@ import java.util.Date
 internal class SocketDataReaderWorker(private val writer: ClientPacketWriter, private val sessionKey: String) : Runnable {
     private val socketData: SocketData = SocketData.instance
 
+    companion object {
+        private const val TAG = "SocketDataReaderWorker"
+    }
+
     override fun run() {
         val session = SessionManager.INSTANCE.getSessionByKey(sessionKey)
         if (session == null) {
@@ -127,6 +131,7 @@ internal class SocketDataReaderWorker(private val writer: ClientPacketWriter, pr
         val data = ByteArray(dataSize)
         System.arraycopy(buffer.array(), 0, data, 0, dataSize)
         session.addReceivedData(data)
+
         // pushing all data to vpn client
         while (session.hasReceivedData()) {
             pushDataToClient(session)
@@ -140,7 +145,7 @@ internal class SocketDataReaderWorker(private val writer: ClientPacketWriter, pr
      */
     private fun pushDataToClient(session: Session) {
         if (!session.hasReceivedData()) {
-            //no data to send
+            // no data to send
             Log.d(TAG, "no data for vpn client")
         }
 
@@ -243,8 +248,4 @@ internal class SocketDataReaderWorker(private val writer: ClientPacketWriter, pr
         }
 
     }
-
-    companion object {
-        private val TAG = "SocketDataReaderWorker"
-    }
 }
diff --git a/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataWriterWorker.kt b/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataWriterWorker.kt
index 51f1194..c9645e5 100755
--- a/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataWriterWorker.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/socket/SocketDataWriterWorker.kt
@@ -18,7 +18,7 @@ import java.util.Date
 class SocketDataWriterWorker(writer: ClientPacketWriter, private val sessionKey: String) : Runnable {
 
     companion object {
-        private val TAG = "SocketDataWriterWorker"
+        private const val TAG = "SocketDataWriterWorker"
         private var writer: ClientPacketWriter? = null
     }
 
diff --git a/app/src/main/java/com/lipisoft/toyshark/socket/SocketNIODataService.kt b/app/src/main/java/com/lipisoft/toyshark/socket/SocketNIODataService.kt
index c08c2e1..ec7a42f 100755
--- a/app/src/main/java/com/lipisoft/toyshark/socket/SocketNIODataService.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/socket/SocketNIODataService.kt
@@ -77,6 +77,7 @@ class SocketNIODataService(private val clientPacketWriter: ClientPacketWriter) :
             if (shutdown) {
                 break
             }
+
             synchronized(syncSelector2) {
                 val iterator = selector!!.selectedKeys().iterator()
                 while (iterator.hasNext()) {
diff --git a/app/src/main/java/com/lipisoft/toyshark/socket/SocketProtector.kt b/app/src/main/java/com/lipisoft/toyshark/socket/SocketProtector.kt
index e6a3bd4..9749d88 100755
--- a/app/src/main/java/com/lipisoft/toyshark/socket/SocketProtector.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/socket/SocketProtector.kt
@@ -63,10 +63,6 @@ class SocketProtector {
         protector!!.protectSocket(socket)
     }
 
-    fun protect(socket: Int) {
-        protector!!.protectSocket(socket)
-    }
-
     fun protect(socket: DatagramSocket) {
         protector!!.protectSocket(socket)
     }
diff --git a/app/src/main/java/com/lipisoft/toyshark/transport/udp/UDPPacketFactory.kt b/app/src/main/java/com/lipisoft/toyshark/transport/udp/UDPPacketFactory.kt
index 29ffaf3..f2cef51 100755
--- a/app/src/main/java/com/lipisoft/toyshark/transport/udp/UDPPacketFactory.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/transport/udp/UDPPacketFactory.kt
@@ -25,13 +25,6 @@ object UDPPacketFactory {
         return UDPHeader(srcPort, destPort, length, checksum)
     }
 
-    fun copyHeader(header: UDPHeader): UDPHeader {
-        return UDPHeader(header.sourcePort,
-                header.destinationPort,
-                header.length,
-                header.checksum)
-    }
-
     /**
      * create packet data for responding to vpn client
      *
diff --git a/app/src/main/java/com/lipisoft/toyshark/util/ByteUtils.kt b/app/src/main/java/com/lipisoft/toyshark/util/ByteUtils.kt
index 26ac2a4..e3ef5ba 100644
--- a/app/src/main/java/com/lipisoft/toyshark/util/ByteUtils.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/util/ByteUtils.kt
@@ -325,7 +325,7 @@ class ByteUtils {
          * @param num target number will be changed
          * @return flipped representation.
          */
-        fun flip16(num: Int): Int {
+        private fun flip16(num: Int): Int {
             return (num and 0x00FF shl 8) + (num and 0xFF00 shr 8)
         }
 
diff --git a/app/src/main/java/com/lipisoft/toyshark/util/PacketUtil.kt b/app/src/main/java/com/lipisoft/toyshark/util/PacketUtil.kt
index 7555eb7..c5d2899 100755
--- a/app/src/main/java/com/lipisoft/toyshark/util/PacketUtil.kt
+++ b/app/src/main/java/com/lipisoft/toyshark/util/PacketUtil.kt
@@ -17,12 +17,10 @@
 package com.lipisoft.toyshark.util
 
 import java.net.Inet4Address
-import java.net.InetAddress
 import java.net.NetworkInterface
 import java.net.SocketException
 import java.nio.ByteBuffer
 import java.nio.ByteOrder
-import java.util.Enumeration
 import android.util.Log
 
 import com.lipisoft.toyshark.network.ip.IPv4Header
@@ -296,7 +294,7 @@ object PacketUtil {
                 "\r\nIP Header length: " + ipheader.ipHeaderLength +
                 "\r\nIP checksum: " + ipheader.headerChecksum +
                 "\r\nMay fragement? " + ipheader.isMayFragment +
-                "\r\nLast fragment? " + ipheader.isLastFragment +
+                "\r\nLast fragment? " + ipheader.lastFragment +
                 "\r\nFlag: " + ipheader.flag +
                 "\r\nFragment Offset: " + ipheader.fragmentOffset +
                 "\r\nDest: " + intToIPAddress(ipheader.destinationIP) +
@@ -346,7 +344,7 @@ object PacketUtil {
                 .append("\r\nTCP Checksum: ").append(tcpheader.checksum)
                 .append("\r\nIs Valid TCP checksum: ").append(isValidChecksum)
                 .append("\r\nMay fragement? ").append(ipHeader.isMayFragment)
-                .append("\r\nLast fragment? ").append(ipHeader.isLastFragment)
+                .append("\r\nLast fragment? ").append(ipHeader.lastFragment)
                 .append("\r\nFlag: ").append(ipHeader.flag.toInt())
                 .append("\r\nFragment Offset: ").append(ipHeader.fragmentOffset.toInt())
                 .append("\r\nWindow: ").append(tcpheader.windowSize)