You need to expose one of your ports - either port 443 (https) or port 80 (http) from your location, for Zoho to push the content of the document.
The saveurl value specified in the HTTPS POST request should to be a proper domain name and publicly accessible over the web.
For Zoho Writer, Sheet and Show -> use 'callback_settings' as parameter and pass 'save_url' value as a key in it.