Establishing a connection to the MQTT broker failed

[saradha92]

I am using this library for my mosquitto mqtt project. When the connection to broker fails it shows some uncaught error. we are working on a project where we will get an email when the connection to broker failed." Trying to catch the error. But it is getting more complicated. If I catch the error it displays another uncaught type error. I'm attaching the image of the type error too.

PHP Fatal error:  Uncaught PhpMqtt\Client\Exceptions\ConnectingToBrokerFailedException: [1000] Establishing a connection to the MQTT broker failed: Socket error [111]: Connection refused in /home/ubuntu1/mqttbroker/vendor/php-mqtt/client/src/MqttClient.php:250
Stack trace:
#0 /home/ubuntu1/mqttbroker/vendor/php-mqtt/client/src/MqttClient.php(161): PhpMqtt\Client\MqttClient->establishSocketConnection()
#1 /home/ubuntu1/mqttbroker/vendor/php-mqtt/client/src/MqttClient.php(145): PhpMqtt\Client\MqttClient->connectInternal()
#2 /home/ubuntu1/mqttbroker/main.php(35): PhpMqtt\Client\MqttClient->connect()
#3 {main}  thrown in /home/ubuntu1/mqttbroker/vendor/php-mqtt/client/src/MqttClient.php on line 250

[Namoshek]

Have you changed something about the code of the MqttClient? Because this looks rather uncommon and I'm not sure how you'd even reach that point.

[saradha92]

No I didn't change anything.

[Namoshek]

In that case, this sounds like a firewall issue. Connection refused means that either the broker is not listening on that port or that a firewall in between is blocking the port. You can verify whether a connection can be established by the device which runs the PHP application with either telnet <host> <port> or openssl s_client -connect <host>:<port> </dev/null. If either of these commands hangs or does give you some kind of refusal response, you should look into your firewall.

[saradha92]

Actually I stopped the broker. As I said earlier I'm working on to get an email notification if the connection to broker fails.So What is supposed to be the output is just this oneline "Establishing connection to broker failed". But why I'm getting this uncaught error and stack traces? Due to this my script is not getting executed properly.

[Namoshek]

I'm not sure what your goal is and what your current solution looks like (i.e. your code), but why don't you simply catch the exception and add some error handling?

try {
    $client = new \PhpMqtt\Client\MqttClient($host, $port, $clientId);
    $client->connect();

    // ... your MQTT logic ...
} catch (\PhpMqtt\Client\Exceptions\ConnectingToBrokerFailedException $e) {
    $this->logger->error('The MQTT client could not connect to the broker.');
    
    // Maybe add something like this as well:
    // $this->notificationManager->sendAlert(...);
}

[saradha92]

I tried catch the error as you mentioned. now I'm getting this error.

PHP Fatal error: Uncaught Error: Cannot access private property PhpMqtt\Client\MqttClient::$logger in /home/ubuntu1/mosquitto/test.php:39

Stack trace:

#0 {main}

thrown in /home/ubuntu1/mosquitto/test.php on line 39

[saradha92]

Fixed the error. Used printf instead of this->logger->error. And put the catch statement at the end of the publish block to avoid further uncaught exceptions.

Thank you so much for the timely response.