phpMQTT connection refused

[Andrew Hickey]

I'm stuck trying to use phpMQTT to publish to a broker.

I have the web script on one server and the MQTT set up on another remote server.

I set up the MQTT server just like this: https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-the-mosquitto-mqtt-messaging-broker-on-centos-7

and I've tested it from the command line with things like:

mosquitto_pub -h mqtt.widgiot.co.uk -t test -m "hello again" -p 8883 --cafile /etc/ssl/certs/ca-bundle.crt -u "[username]" -P "[password]"

and it works great. Message received

But from the phpMQTT I'm just getting this in my error logs:

PHP Warning:  stream_socket_client(): unable to connect to tls://mqtt.widgiot.co.uk:8883 (Connection refused)...

This is the function that uses mqtt:

public function onUserLoginFailure($response)

{

require("phpMQTT/phpMQTT.php");

        $server = "mqtt.widgiot.co.uk";    

        $port = 8883;                   

        $username = "[username]";            

        $password = "[password]";               

        $client_id = "phpMQTT-publisher";

        $cafile = '/etc/ssl/certs/ca-bundle.crt';

        $mqtt = new phpMQTT($server, $port, $client_id , $cafile);

        if ($mqtt->connect(true, NULL, $username, $password)) {

            $mqtt->publish("test", "Hello World! at " . date("r"), 0);

            $mqtt->close();

        } else {

            echo "Time out!\n";

        }

}

The username/password details are correct. I'm just not sure about how to reference the $cacert. I've used the same location as in the terminal (which works). 

Any ideas what might be the issue? Firewall? How to check where the blockage is coming from? I have root access on both servers (the one with the phpmqtt script and the mqtt broker server).