The first (and most likely) issue is that the firewall at your host forbids the outgoing connection.
The easiest way to solve that is to change the API port to 443 or 80, since firewalls usually allow HTTP and HTTPS connections. Alternatively, you can contact your host, and ask them to enable outgoing connections to port 8728.
In addition, you’re having an old PHP version - 5.2.17, which may be older than the one on your computer. You may want to (ask your host to) upgrade to a newer PHP version (at least 5.3.0), and in fact, if you’re using this client, you must.