Guidance for migration from the old PhantomJS based export server?

I have an old ASP.net WebForms site that is still using the PhantomJS based highcharts export server. The code sends the highcharts definition JavaScript via HTTP POST to the old export server listening on port 3003.

I really need to get that code migrated to use the new node-export-server so I can run it the export server in a container on linux. Is there any difference in usage from the client code standpoint? If so, is there a written guide that describes the changes in the interface?