Cross domain asynchronous multipart POST file uploads using flXHR?

I am building a "widget" that can be embedded in other people's websites, that talk back to my server.

Right now I am using flXHR for the cross domain asynchronous communication, and it works fine for doing GETs inside the widget.

However the major point of the widget is to allow clients to submit a form back to my server, complete with some multipart POST data (eg, the html file upload field). I need some kind of 开发者_开发知识库cross domain asynchronous file upload.

I can't figure out how to attach the multipart file data to the flXHR request. Is this even possible?

As far as I know, no, you can't attach file data to a flXHR POST... you'd have to have a flash component that was built to be a file uploader to do the file part of the upload, and could use flXHR for the rest of the form data.