diff --git a/docs/zh-cn/README.md b/docs/zh-cn/README.md
index 2304abb..1074459 100644
--- a/docs/zh-cn/README.md
+++ b/docs/zh-cn/README.md
@@ -20,21 +20,13 @@ composer require simps/mqtt
 
 参考 [examples](https://github.com/simps/mqtt/tree/master/examples) 目录
 
-## 捐献及赞助 :id=donate
+## 关注
 
-### 一次性赞助
+![](https://cdn.jsdelivr.net/gh/sy-records/staticfile/images/202012/wechat_white.png)
 
-如果您是个人开发者并且 PHPMQTT 给您解决燃眉之急或带来些许明朗，您可以打赏一杯咖啡或一杯香茗 :)
+## 赞赏 :id=donate
 
-我们通过以下方式接受赞助：
+如果给您解决燃眉之急或带来些许明朗，您可以打赏一杯咖啡或一杯香茗 :)
 
-![alipay](https://cdn.jsdelivr.net/gh/sy-records/staticfile/images/alipay.jpg ':size=362x562')
-![wechat](https://cdn.jsdelivr.net/gh/sy-records/staticfile/images/wechatpay.png ':size=autox562')
+[donate](https://donate.qq52o.me/ ':include :type=iframe')
 
-### 周期性赞助
-
-如果您是企业经营者并且将 PHPMQTT 用在商业产品中，那么赞助 PHPMQTT 有商业上的益处：可以让您的产品所依赖的类库保持健康并得到积极的升级维护，也能获得一些技术支持。
-
-周期性赞助可以获得额外的回报，比如您的名字或组织/公司 Logo 及链接会出现在 PHPMQTT 的 GitHub 仓库中。
-
-> 如您希望为 PHPMQTT 提供周期性的赞助，可邮件至 lufei@simps.io
diff --git a/examples/getLevel.php b/examples/getLevel.php
new file mode 100644
index 0000000..1f7ee20
--- /dev/null
+++ b/examples/getLevel.php
@@ -0,0 +1,51 @@
+<?php
+/**
+ * This file is part of Simps
+ *
+ * @link     https://github.com/simps/mqtt
+ * @contact  Lu Fei <lufei@simps.io>
+ *
+ * For the full copyright and license information,
+ * please view the LICENSE file that was distributed with this source code
+ */
+
+include __DIR__ . '/bootstrap.php';
+
+use Simps\MQTT\Protocol\Types;
+use Simps\MQTT\Protocol\V3;
+use Simps\MQTT\Protocol\V5;
+use Simps\MQTT\Tools\UnPackTool;
+use Simps\MQTT\Protocol\ProtocolInterface;
+
+$server = new Swoole\Server('127.0.0.1', 1883, SWOOLE_BASE);
+
+$server->set(
+    [
+        'open_mqtt_protocol' => true,
+        'worker_num' => 1,
+        'package_max_length' => 2 * 1024 * 1024,
+    ]
+);
+
+$server->on('connect', function ($server, $fd) {
+    echo "Client #{$fd}: Connect.\n";
+});
+
+$server->on('receive', function (Swoole\Server $server, $fd, $from_id, $data) {
+    $type = UnPackTool::getType($data);
+    if ($type === Types::CONNECT) {
+        $level = UnPackTool::getLevel($data);
+        $class = $level === ProtocolInterface::MQTT_PROTOCOL_LEVEL_5_0 ? V5::class : V3::class;
+        $server->fds[$fd] = ['level' => $level, 'class' => $class];
+    }
+    /** @var ProtocolInterface $unpack */
+    $unpack = $server->fds[$fd]['class'];
+    var_dump($unpack::unpack($data));
+});
+
+$server->on('close', function ($server, $fd) {
+    unset($server->fds[$fd]);
+    echo "Client #{$fd}: Close.\n";
+});
+
+$server->start();
diff --git a/src/Tools/UnPackTool.php b/src/Tools/UnPackTool.php
index 678dfa7..2da2b88 100644
--- a/src/Tools/UnPackTool.php
+++ b/src/Tools/UnPackTool.php
@@ -13,7 +13,9 @@
 
 namespace Simps\MQTT\Tools;
 
+use Simps\MQTT\Exception\InvalidArgumentException;
 use Simps\MQTT\Exception\LengthException;
+use Simps\MQTT\Protocol\Types;
 
 class UnPackTool extends Common
 {
@@ -97,4 +99,21 @@ public static function getRemaining(string $data): string
 
         return substr($data, $headBytes, $remainingLength);
     }
+
+    /**
+     * Get the MQTT protocol level.
+     */
+    public static function getLevel(string $data): int
+    {
+        $type = static::getType($data);
+
+        if ($type !== Types::CONNECT) {
+            throw new InvalidArgumentException(sprintf('packet must be of type connect, %s given', Types::getType($type)));
+        }
+
+        $remaining = static::getRemaining($data);
+        $length = unpack('n', $remaining)[1];
+
+        return ord($remaining[$length + 2]);
+    }
 }
diff --git a/tests/Unit/ToolsTest.php b/tests/Unit/ToolsTest.php
new file mode 100644
index 0000000..0634df1
--- /dev/null
+++ b/tests/Unit/ToolsTest.php
@@ -0,0 +1,47 @@
+<?php
+/**
+ * This file is part of Simps
+ *
+ * @link     https://github.com/simps/mqtt
+ * @contact  Lu Fei <lufei@simps.io>
+ *
+ * For the full copyright and license information,
+ * please view the LICENSE file that was distributed with this source code
+ */
+
+declare(strict_types=1);
+
+namespace SimpsTest\MQTT\Unit;
+
+use PHPUnit\Framework\TestCase;
+use Simps\MQTT\Exception\InvalidArgumentException;
+use Simps\MQTT\Protocol\ProtocolInterface;
+use Simps\MQTT\Tools\UnPackTool;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+class ToolsTest extends TestCase
+{
+    public function testGetLevel()
+    {
+        $connect_31 = '104400064d51497364700306000a001353696d70735f36313362316164323236626334001973696d70732d6d7174742f757365723030312f64656c6574650006627965627965';
+        $connect_311 = '104200044d5154540406000a001353696d70735f36313362313830323035636633001973696d70732d6d7174742f757365723030312f64656c6574650006627965627965';
+        $connect_50 = '106200044d515454050e000a0b110000003c21ffff22ffff001353696d70735f3631336231613330313962663213180000003c020000003c030004746573740101001973696d70732d6d7174742f757365723030312f64656c6574650006627965627965';
+        $this->assertSame(UnPackTool::getLevel(hex2bin($connect_31)), ProtocolInterface::MQTT_PROTOCOL_LEVEL_3_1);
+        $this->assertSame(UnPackTool::getLevel(hex2bin($connect_311)), ProtocolInterface::MQTT_PROTOCOL_LEVEL_3_1_1);
+        $this->assertSame(UnPackTool::getLevel(hex2bin($connect_50)), ProtocolInterface::MQTT_PROTOCOL_LEVEL_5_0);
+    }
+
+    public function testInvalidGetLevel()
+    {
+        try {
+            $connAck = '200200';
+            UnPackTool::getLevel(hex2bin($connAck));
+        } catch (\Throwable $ex) {
+            $this->assertInstanceOf(InvalidArgumentException::class, $ex);
+            $this->assertSame($ex->getMessage(), 'packet must be of type connect, connack given');
+        }
+    }
+}