The error message is showing that your connection to the host adtwtipwvsds01.tawazun.ae is being refused. I assume thats the hostname of your Windchill server. Are your clients able to make direct RMI connections to your Windchill server, or is there a firewall blocking the RMI ports? If the RMI ports are being blocked, then you'll need to tunnel the RMI traffic over HTTP instead. You can find instructions for RMI tunneling here:
https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS66009