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MQTT 是一种基于发布/订阅模式的 轻量级物联网消息传输协议 ，可以用极少的代码和带宽为联网设备提供实时可靠的消息服务，它广泛应用于物联网、移动互联网、智能硬件、车联网、电力能源等行业。

本文主要介绍如何在 PHP项目中使用composer require php-mqtt/client库 ，实现客户端与 MQTT 服务器 的连接、订阅、收发消息等功能。

<?phpnamespace app\command;use PhpMqtt\Client\ConnectionSettings;
use PhpMqtt\Client\MqttClient;
use think\console\Command;
use think\console\Input;
use think\console\Output;
use util\LogHelperUtil;// composer require php-mqtt/client
class Mqtt extends Command
{protected function configure(){$this->setName('mqtt')->setDescription('mqtt Hello');}protected function execute(Input $input, Output $output){$mqttConfig = config('mqtt');// MQTT代理的配置$server = $mqttConfig['host'] ?? ''; // MQTT代理的地址$port = $mqttConfig['port'] ?? 1883; // MQTT代理的端口$username = 'test_mqtt'; // MQTT代理的用户名（如果需要）$password = '123456'; // MQTT代理的密码（如果需要）$clientId = 'service-mqtt-' . time(); // 客户端IDtry {// 创建MQTT客户端实例$mqtt = new MqttClient($server, intval($port), $clientId);$settings = (new ConnectionSettings())->setUsername($username)->setPassword($password)->setKeepAliveInterval(10)   // 根据需要设置心跳间隔->setReconnectAutomatically(true) // 是否会尝试自动重新连接->setDelayBetweenReconnectAttempts(2000) // 定义重新连接尝试之间的延迟（毫秒）。->setMaxReconnectAttempts(10); // 重新连接的最大尝试次数$mqtt->connect($settings); // 连接到MQTT代理// 订阅一个主题$topic = 'testtopic/#';$mqtt->subscribe($topic, function ($topic, $message) use ($mqtt) {$time = self::getTime("Y年m月d日G时i分s秒x毫秒");echo "{$time} 主题：{$topic} - 收到：" . ($message) . PHP_EOL;if ($topic != 'testtopic/service/2' && $topic != 'testtopic/golang') {$mqtt->publish('testtopic/service/2', "hello[{$topic}]", 2, true);}}, 2);// 保持脚本运行，以便接收消息
//            while ($mqtt->isConnected()) {
//                $mqtt->loop();
//            }$mqtt->loop();
//            $mqtt->disconnect(); // 断开连接} catch (\Exception $e) {echo "MQTT Error: " . $e->getMessage();}$output->writeln("Received message on topic");}private static function getTime($tag){list($usec, $sec) = explode(" ", microtime());$now_time = $sec . '.' . substr($usec, 2, 4);list($usec, $sec) = explode(".", $now_time);$date = date($tag, $usec);return str_replace('x', $sec, $date);}
}