故障代码：HTTP字符串：无法连接到主机

When trying to get the FEDEX rate using a SOAP request (I'm using PHP with XAMPP), I'm getting the following error:

Fault

Code:HTTP String:Could not connect to host

in this code:

<?php 

    require_once('library/fedex-common.php');

    $path_to_wsdl = "wsdl/RateService_v13.wsdl";     
    ini_set("soap.wsdl_cache_enabled", "0"); 

    $client = new SoapClient($path_to_wsdl, array('trace' => 1)); 
    try { 
        if(setEndpoint('changeEndpoint')) { 
            $newLocation = $client->__setLocation(setEndpoint('endpoint')); 
        } 
        $response = $client ->getRates($request); 
    } catch (SoapFault $exception) { 
        printFault($exception, $client); 
    }

?>

This happens on Ubuntu only. The same code (also using XAMPP) works fine on Windows, however.