Posting files with Ajax

"Many people say uploading files with AJAX is impossible! Well, they're wrong :-)
Granted this solution only works with FireFox/Mozilla. And the user has to change a setting in "about:config" and accept the advanced access privileg..."


This is all that I could find on the net for ways to upload files using ajax. Lately I've been a huge fan of sockets and I know how to send post data to a server using it, now I'm wondering if it would be possible to submit files in a similar fashion, i.e. submiting multipart/form-data instead of the other default.

Is there anyone that could shed some light on writing to a socket that would post to a php script, with the content type as multipart/form-data?