How does IE downloading is achieved?

I often click on a file link in the IE and a download box just pops out. But what happens behind this scene? I know that IE always talks to web server with HTTP protocol, and HTTP is text based.

So is IE download achieved with HTTP protocol? If so, how could a开发者_JS百科rbitrary file format be downloaded over a text based protocol?

And I am currently trying to make a web app which will direct my customer to download some file. My current design is to implement a web service. Customer will call this web service and the web service will return the file download URL. But then I don't know what to do with the URL. Could I just use something like File.Copy to copy the file from the URL to local disk? Or how should I treat the URL? If there's a better design, please teach me.

Many thanks...

By specifying the right content type, you can tell the browser what kind of data it is you are sending. In addition, there are special encodings (like Base 64) that allow binary content to be displayed as text, using only a limited set of characters and escaping everything else.

Then, there is nothing you need to do with the url. IE will know whether it can or cannot open the file and will show the download box accordingly.

maybe it's like

<?php
// We'll be outputting a PDF
header('Content-type: application/pdf');

// It will be called downloaded.pdf
header('Content-Disposition: attachment; filename="downloaded.pdf"');

// The PDF source is in original.pdf
readfile('original.pdf');
?>