diff --git a/lib/resolver.php b/lib/resolver.php
index 579b10b..4beeb53 100644
--- a/lib/resolver.php
+++ b/lib/resolver.php
@@ -15,6 +15,17 @@ include_once("utils.php");
  
  - Could use some more test-cases, especially error ones
 */
+class ResolveResult {
+	const Ok = 0;
+	const EmptyRequest = 1;
+	const RequestNotAString = 2;
+	const RequestContainsInvalidChar = 3;
+	const RequestContainsPathWalk = 4;
+	const FileNotFound = 5;
+	const InvalidFilename = 6;
+	const InvalidPath = 7;
+}
+
 class Resolver {
 	private $isDirty = FALSE;
 	private $cache = array();
@@ -33,21 +44,31 @@ class Resolver {
 	function __destruct() {
 		// $this->printCache()
 		if ($this->isDirty) {
+			if (!is_writable($this->config['main']['cache_filename'])) {
+				$this->log_error_and_throw("Could not write to file '".$this->config['cache_filename']."' at Resolver::destruct");
+			}
 			if (!file_put_contents($this->config['main']['cache_filename'], serialize($this->cache))) {
 				$this->log_error_and_throw("Could not write to file '".$this->config['cache_filename']."' at Resolver::destruct");
 			}
 		}
 	}
-	function log_error_and_throw($message) {
-		global $logger;
-		$logger->log('LOG_ERROR', $message);
-		throw new Exception($message);
-	}
-	function log_debug($message) {
+	
+	public function log_debug($message) {
 		global $logger;
 		$logger->log('LOG_DEBUG', $message);
 	}
-	function searchForFile($filename) {
+
+	public function log_error($message) {
+		global $logger;
+		$logger->log('LOG_ERROR', $message);
+	}
+
+	public function log_error_and_throw($message) {
+		$this->log_error($message);
+		throw new Exception($message);
+	}
+	
+	public function searchForFile($filename) {
 		foreach($this->config['subdirs'] as $key => $value) {
 			if ($key === "firmware" || $key === "tftproot" ) {
 				continue;
@@ -58,9 +79,11 @@ class Resolver {
 				 return $path;
 			}
 		}
-		$this->log_error_and_throw("File '$filename' does not exist");
+		$this->log_error("File '$filename' does not exist");
+		return ResolveResult::FileNotFound;
 	}
-	function buildCleanCache() {
+	
+	public function buildCleanCache() {
 		foreach($this->config['subdirs'] as $key =>$value) {
 			if ($key === "tftproot") {
 				continue;
@@ -81,50 +104,66 @@ class Resolver {
 		}
 		$this->isDirty  = TRUE;
 	}
-	function addFile($requestpath, $truepath) {
-		//$this->logger->log('LOG_DEBUG', "Adding $requestpath");
+	
+	public function addFile($requestpath, $truepath) {
 		$this->log_debug("Adding $requestpath");
 		$this->cache[$requestpath] = $truepath;
 		$this->isDirty  =TRUE;
 	}
-	function removeFile($requestpath) {
+	
+	public function removeFile($requestpath) {
 		$this->log_debug("Removing $hash");
 		unset($this->cache[$requestpath]);
 		$this->isDirty = TRUE;
 	}
-	function validateRequest($request) {
+	
+	public function validateRequest($request) {
 		/* make sure request does not startwith or contain: "/", "../" or "/./" */
 		/* make sure request only starts with filename or one of $config[$subdir]['locale'] or $config[$subdir]['wallpaper'] */
 		/* check uri/url decode */
+		if (!$request || empty($request)) {
+			$this->log_error("Request is empty");
+			return ResolveResult::EmptyRequest;
+		}
 		if (!is_string($request)) {
-			$this->log_error_and_throw("Request is not a string");
+			$this->log_error("Request is not a string");
+			return ResolveResult::RequestNotAString;
 		}
 		$this->log_debug($request . ":" . escapeshellarg($request) . ":" . utf8_urldecode($request) . "\n");
 		$escaped_request = escapeshellarg(utf8_urldecode($request));
 		if ($escaped_request !== "'" . $request . "'") {
-			$this->log_error_and_throw("Request '$request' contains invalid characters");
+			$this->log_error("Request '$request' contains invalid characters");
+			return ResolveResult::RequestContainsInvalidChar;
 		}
 		if (strstr($escaped_request, "..")) {
-			$this->log_error_and_throw("Request '$request' containst '..'");
+			$this->log_error("Request '$request' contains '..'");
+			return ResolveResult::RequestContainsPathWalk;
 		}
+		return ResolveResult::Ok;
 	}
-	function resolve($request) /* canthrow */ {
-		$this->validateRequest($request);
+
+	public function resolve($request) /* canthrow */ {
 		$path = '';
+		$result = $this->validateRequest($request);
+		if ($result !== ResolveResult::Ok) {
+			return $result;
+		}
 		if (array_key_exists($request, $this->cache)) {
 			if ($path = $this->cache[$request]) {
 				if (!file_exists($path)) {
 					 $this->removeFile($request);
-					 $this->log_error_and_throw("File '$request' does not exist on FS");
+					 $this->log_error("File '$request' does not exist on FS");
+					 return ResolveResult::FileNotFound;
 				}
 				return $path;
 			}
 		}
 		if ($this->searchForFile($request)) {
-			return $this->cache[$request];
+			$path = $this->cache[$request];
 		}
 		return $path;
 	}
+	
 	/* temporary */
 	function printCache() {
 		print_r($this->cache);
@@ -134,32 +173,36 @@ class Resolver {
 // Testing
 if(defined('STDIN') ) {
 	$resolver = new Resolver($config);
-
 	$test_cases = Array(
-		Array('request' => 'jar70sccp.9-4-2ES26.sbn', 'expected' => '/tftpboot/firmware/7970/jar70sccp.9-4-2ES26.sbn', 'throws' => FALSE),
-		Array('request' => 'Russian_Russian_Federation/be-sccp.jar', 'expected' => '/tftpboot/locales/languages/Russian_Russian_Federation/be-sccp.jar', 'throws' => FALSE),
-		Array('request' => 'Spain/g3-tones.xml', 'expected' => '/tftpboot/locales/countries/Spain/g3-tones.xml', 'throws' => FALSE),
-		Array('request' => '320x196x4/Chan-SCCP-b.png', 'expected' => '/tftpboot/wallpapers/320x196x4/Chan-SCCP-b.png', 'throws' => FALSE),
-		Array('request' => 'XMLDefault.cnf.xml', 'expected' => '/tftpboot/settings/bak/XMLDefault.cnf.xml', 'throws' => FALSE),
-		Array('request' => '../XMLDefault.cnf.xml', 'expected' => '', 'throws' => TRUE),
-		Array('request' => 'XMLDefault.cnf.xml/../../text.xml', 'expected' => '', 'throws' => TRUE),
-		
+		Array('request' => 'jar70sccp.9-4-2ES26.sbn', 'expected' => '/tftpboot/firmware/7970/jar70sccp.9-4-2ES26.sbn'),
+		Array('request' => 'Russian_Russian_Federation/be-sccp.jar', 'expected' => '/tftpboot/locales/languages/Russian_Russian_Federation/be-sccp.jar'),
+		Array('request' => 'Spain/g3-tones.xml', 'expected' => '/tftpboot/locales/countries/Spain/g3-tones.xml'),
+		Array('request' => '320x196x4/Chan-SCCP-b.png', 'expected' => '/tftpboot/wallpapers/320x196x4/Chan-SCCP-b.png'),
+		Array('request' => 'XMLDefault.cnf.xml', 'expected' => '/tftpboot/settings/bak/XMLDefault.cnf.xml'),
+		Array('request' => '../XMLDefault.cnf.xml', 'expected' => ResolveResult::RequestContainsPathWalk),
+		Array('request' => 'XMLDefault.cnf.xml/../../text.xml', 'expected' => ResolveResult::RequestContainsPathWalk),
 	);
 	foreach($test_cases as $test) {
 		try {
 			$result = $resolver->resolve($test['request']);
-			if ($result !== $base_path . $test['expected']) {
-				print("Error: expected result does not match what we got\n");
-				print("request:'".$test['request']."', result:'" . $base_path . $test['expected'] . "'\n");
+			if (is_string($result)) {
+				if ($result === $base_path . $test['expected']) {
+					print("'" . $test['request'] . "' => '" . $result . "'\n");
+					continue;
+				}
 			} else {
-				print("'" . $test['request'] . "' => '" . $result . "'\n");
+				if ($result === $test['expected']) {
+					print("'" . $test['request'] . "' => '" . $result . "'\n");
+					continue;
+				}
 			}
+			print("Error: expected result does not match what we got\n");
+			print("request:'".$test['request']."'\n");
+			print("expected:'" . $base_path . $test['expected'] . "'\n");
+			print("result:'" . $result . "'\n\n");
 		} catch (Exception $e) {
-			if (!$test['throws']) {
-				print("Error: request was expected to throw: $e\n");
-			} else {
-				print("'" . $test['request'] . "' => throws error as expected\n");
-			}
+			print("'" . $test['request'] . "' => throws error as expected\n");
+			print("Exception: " . $e->getMessage() . "\n");
 		}
 	}
 	unset($resolver);
diff --git a/tftp_provisioner.php b/tftp_provisioner.php
index 8d21f94..a33f692 100755
--- a/tftp_provisioner.php
+++ b/tftp_provisioner.php
@@ -8,7 +8,7 @@ class TFTPProvisioner extends TFTPServer
 {
   private $_debug;
   private $_resolver;
-  private $_filename;
+  private $_settings_path;
 
   function __construct($server_url, $config, $logger = NULL, $debug = false)
   {
@@ -20,42 +20,32 @@ class TFTPProvisioner extends TFTPServer
     $this->_debug = $debug;
     $this->max_put_size = 60000000;
     $this->_resolver = new Resolver($config);
-  }
-
-  public function exists($peer, $req_filename)
-  {
-    if (($this->_filename = $this->_resolver->resolve($req_filename))) {
-      return file_exists($this->_filename);
-    }
-    return false;
-  }
-
-  public function readable($peer, $req_filename)
-  {
-    return is_readable($this->_filename);
-  }
-
-  public function get($peer, $req_filename, $mode)
-  {
-    return file_get_contents($this->_filename);
+    $this->_settings_path = $this->_config['main']['base_path'] . DIRECTORY_SEPARATOR
+                . $this->_config['subdirs']['settings']['path'] . DIRECTORY_SEPARATOR;
   }
 
   public function writable($peer, $req_filename)
   {
-    // check $req_filename starts with 'settings/' (SPA phones can write to tftpboot)
-    $settings_path = $this->_config['main']['base_path'] . DIRECTORY_SEPARATOR
-                . $this->_config['subdirs']['settings']['path'] . DIRECTORY_SEPARATOR;
-    $filename = $settings_path . basename($req_filename);
-    if (is_writable($filename) || (!file_exists($filename) && is_writable($settings_path))) {
-      $this->_filename = $filename;
-      return true;
+    $filename = $this->_settings_path . basename($req_filename);
+    if (file_exists($filename)) {
+      return is_writable($filename);
     }
+    return is_writable($this->_settings_path);
+  }
+
+  public function get($peer, $req_filename, $mode)
+  {
+    $filename = $this->_resolver->resolve($req_filename);
+    if (file_exists($filename) && is_readable($filename))
+      return file_get_contents($filename);
     return false;
   }
 
-  public function put($peer, $filename, $mode, $content)
+  public function put($peer, $req_filename, $mode, $content)
   {
-    return file_put_contents($this->_filename, $content);
+    // (SPA phones can write to tftpboot -> redirect PUT request to 'settings' folder)
+    $filename = $this->_settings_path . basename($req_filename);
+    return file_put_contents($filename, $content);
   }
 
   /*