Fix code style issues

mobile/src/main/java/com/github/shadowsocks/bg/VpnService.kt

@@ -38,6 +38,7 @@ import com.github.shadowsocks.utils.Subnet
 import com.github.shadowsocks.utils.parseNumericAddress
 import java.io.File
 import java.io.FileDescriptor
+import java.io.IOException
 import java.lang.reflect.Method
 import java.util.*
 import android.net.VpnService as BaseVpnService
@@ -55,18 +56,24 @@ class VpnService : BaseVpnService(), LocalDnsService.Interface {
         override val socketFile: File = File(app.deviceContext.filesDir, "protect_path")
 
         override fun accept(socket: LocalSocket) {
+            var success = false
             try {
                 socket.inputStream.read()
                 val fds = socket.ancillaryFileDescriptors
                 if (fds.isEmpty()) return
                 val fd = getInt.invoke(fds.first()) as Int
-                val ret = protect(fd)
+                success = protect(fd)
                 JniHelper.close(fd) // Trick to close file decriptor
-                socket.outputStream.write(if (ret) 0 else 1)
             } catch (e: Exception) {
                 Log.e(tag, "Error when protect socket", e)
                 app.track(e)
             }
+            try {
+                socket.outputStream.write(if (success) 0 else 1)
+            } catch (e: IOException) {
+                Log.e(tag, "Error when returning result in protect", e)
+                app.track(e)
+            }
         }
     }
     class NullConnectionException : NullPointerException()
@@ -118,7 +125,7 @@ class VpnService : BaseVpnService(), LocalDnsService.Interface {
         super.startNativeProcesses()
 
         val fd = startVpn()
-        if (!sendFd(fd)) throw Exception("sendFd failed")
+        if (!sendFd(fd)) throw IOException("sendFd failed")
     }
 
     override fun buildAdditionalArguments(cmd: ArrayList<String>): ArrayList<String> {