diff --git a/src/Client.php b/src/Client.php
index d6a41a9..70c33fd 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -12,7 +12,7 @@
 use \InvalidArgumentException;
 use RuntimeException;
 
-class Client implements ConnectorInterface
+final class Client implements ConnectorInterface
 {
     /**
      *
diff --git a/src/Server.php b/src/Server.php
index 2bc4723..cc41f1f 100644
--- a/src/Server.php
+++ b/src/Server.php
@@ -15,7 +15,7 @@
 use \Exception;
 use React\Promise\Timer\TimeoutException;
 
-class Server
+final class Server
 {
     // the following error codes are only used for SOCKS5 only
     /** @internal */
@@ -35,7 +35,7 @@ class Server
     /** @internal */
     const ERROR_ADDRESS_UNSUPPORTED = 0x08;
 
-    protected $loop;
+    private $loop;
 
     private $connector;
 
@@ -104,6 +104,7 @@ public function unsetAuth()
         $this->auth = null;
     }
 
+    /** @internal */
     public function onConnection(ConnectionInterface $connection)
     {
         $that = $this;
@@ -118,7 +119,9 @@ public function onConnection(ConnectionInterface $connection)
     }
 
     /**
-     * gracefully shutdown connection by flushing all remaining data and closing stream
+     * [internal] gracefully shutdown connection by flushing all remaining data and closing stream
+     *
+     * @internal
      */
     public function endConnection(ConnectionInterface $stream)
     {
@@ -179,6 +182,7 @@ private function handleSocks(ConnectionInterface $stream)
         });
     }
 
+    /** @internal */
     public function handleSocks4(ConnectionInterface $stream, $protocolVersion, StreamReader $reader)
     {
         // suppliying hostnames is only allowed for SOCKS4a (or automatically detected version)
@@ -235,6 +239,7 @@ public function handleSocks4(ConnectionInterface $stream, $protocolVersion, Stre
         });
     }
 
+    /** @internal */
     public function handleSocks5(ConnectionInterface $stream, $auth=null, StreamReader $reader)
     {
         $remote = $stream->getRemoteAddress();
@@ -344,6 +349,7 @@ public function handleSocks5(ConnectionInterface $stream, $auth=null, StreamRead
         });
     }
 
+    /** @internal */
     public function connectTarget(ConnectionInterface $stream, array $target)
     {
         $uri = $target[0];
diff --git a/src/StreamReader.php b/src/StreamReader.php
index 6dbf51c..f01d252 100644
--- a/src/StreamReader.php
+++ b/src/StreamReader.php
@@ -9,7 +9,7 @@
 /**
  * @internal
  */
-class StreamReader
+final class StreamReader
 {
     const RET_DONE = true;
     const RET_INCOMPLETE = null;