Php-mqtt no received message

please help me, why I don’t receive a message after publish, all login, submit details are correct. I send the data, but I do not receive the return message..

try {
        // Create a new instance of an MQTT client and configure it to use the shared broker host and port.
        $client = new MqttClient($host, 1883, $clientID, MqttClient::MQTT_3_1, null);
    
        // Create and configure the connection settings as required.
        $connectionSettings = (new ConnectionSettings)
                ->setUsername($username)
                ->setPassword($password);
    
        // Connect to the broker with the configured connection settings and with a clean session.
        $client->connect($connectionSettings, true);
    
        $handler = function (MqttClient $client, $topic, $message, $messageId, int $qualityOfService, bool $retain) use ($logger) {
           
            
            //Missing received msg
        };
        $client->registerPublishEventHandler($handler);
    
    
        // Publish the message 'Hello world!' on the topic 'foo/bar/baz' using QoS 0.
        $client->publish($topic, $msg, MqttClient::QOS_AT_MOST_ONCE);
    
    
    
        // Gracefully terminate the connection to the broker.
        $client->disconnect();
    } catch (MqttClientException $e) {
        // MqttClientException is the base exception of all exceptions in the library. Catching it will catch all MQTT related exceptions.
        echo "no connected";
    }