PHP JasperReports Server API Error

I am trying to ultimately run and display reports from a remote Jasper Server in a PHP application. What I am trying to do this with is the jrs-rest-php-client project on github.

The error:

Fatal error: Uncaught exception 'Jaspersoft\Exception\RESTRequestException' with message 'An unexpected HTTP status code was returned by the server' in C:\xampp\htdocs\jrs\vendor\src\Jaspersoft\Tool\RESTRequest.php:409 
Stack trace: 
#0 C:\xampp\htdocs\jrs\vendor\src\Jaspersoft\Tool\RESTRequest.php(479): Jaspersoft\Tool\RESTRequest->handleError(0, Array, false) 
#1 C:\xampp\htdocs\jrs\vendor\src\Jaspersoft\Service\ReportService.php(40): Jaspersoft\Tool\RESTRequest->prepAndSend('https://jasper....', Array, 'GET', NULL, true) 
#2 C:\xampp\htdocs\jrs\report.php(30): Jaspersoft\Service\ReportService->runReport('/Reports/Distri...', 'html') 
#3 {main} thrown in C:\xampp\htdocs\jrs\vendor\src\Jaspersoft\Tool\RESTRequest.php on line 409

My PHP:

require_once __DIR__ . "/vendor/autoload.php";
use Jaspersoft\Client\Client;
$d = new Client(
    "http://jasper.server.com/jasperserver-pro",
    "username",
    "password",
    "organization"
);  
$info = $d->serverInfo();

Any ideas?

Looking into the code of RESTRequest.php there are two cases in which this exception is thrown:

A JSON result set with an unknown error code is returned (unknown meaning different from 200 OK)
No JSON result set is returned at all

So I suspect the connection isn't working properly. To find out more, you should catch the exception in your code and evaluate it:

It could look something like this (I'm more familiar with Java):

try {
    $d = new Client(
        "http://jasper.server.com/jasperserver-pro",
        "username",
        "password",
        "organization"
    );  

    $info = $d->serverInfo();

} catch (RESTRequestException $e) {
    echo 'RESTRequestException:';
    echo 'Exception message:   ',  $e->getMessage(), "\n";
    echo 'Set parameters:      ',  $e->parameters, "\n";
    echo 'Expected status code:',  $e->expectedStatusCodes, "\n";
    echo 'Error code:          ',  $e->errorCode, "\n";
}

If there is still an error, you can check the following:

Can you reach the jasper server from the server where this code is deployed? Sometimes e.g. firewall settings can interfere.
Is the organization called exactly like defined in the properties of the organization in the server? (Open repository / right click on organization / properties / resource-id)