The document editing service informs the document storage service about the status of the document editing and sends the response with all the necessary data via the callbackUrl, which is specified in the configuration file like this:
var docEditor = new DocsAPI.DocEditor("placeholder", {
"editorConfig": {
"callbackUrl": "https://example.com/url-to-callback.ashx"
},
...
});
Here the https://example.com/url-to-callback.ashx is the address of the special handler which can process the response from the document editing service and response with the "error": 0 status code. This handler can be written in the programming language of your choice.
All the parameters which can be sent to the callback handler and their description can be found at this page.
There are also examples in several programming languages of how this handler can be implemented: .Net (C#), Java, Node.js, PHP, Ruby.