the websocket service api is intended for PC usage. If your purpose is to enable call control functions to your deskphone i suggest you look into;
if your phone has an USB port;
USB HID specification or our Linux SDK (if your phone is based on Linux platform).
<a href="https://jabra.wpengine.com/windows/">USB HID at bottom</a>
w/o USB port e.g. if your phone has a 8-pin AUX port;
Take a Look at our Jabra IQ protocol;
<a href="https://jabra.wpengine.com/deskphones/">Jabra IQ</a>
please let me know if you have further queries.