check that network connection exists at application start

app/src/main/kotlin/com/tutpro/baresip/Utils.kt

@@ -3,6 +3,8 @@ package com.tutpro.baresip
 import android.content.Context
 import android.support.v7.app.AlertDialog
 import android.util.Log
+import android.net.ConnectivityManager
+import android.net.NetworkInfo
 
 import java.io.*
 
@@ -115,6 +117,17 @@ object Utils {
         return res
     }
 
+    fun isConnected(context: Context): Boolean {
+        val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+        val activeNetwork = cm.activeNetworkInfo
+        if (activeNetwork != null && activeNetwork.isConnected) {
+            val networkType = activeNetwork.type
+            return networkType == ConnectivityManager.TYPE_WIFI || networkType == ConnectivityManager.TYPE_MOBILE
+        } else {
+            return false
+        }
+    }
+
     external fun cmd_exec(cmd: String): Int
     external fun uri_decode(uri: String): Boolean
     external fun audio_codecs(): String