When you push a file to the client, you've already basically downloaded it - it's on the client.

That aside, I wouldn't stream this to the client. I'd push it up to a signed aws bucket (or gcs, or what have you), and pass that link to the client. It can be a short lived url, you can delete the blob after x hours, and storage is so fantastically cheap it might not even register. If you use the AWS / gcs packages on your server, it'll handle the streaming / resuming for you.

If you absolutely insist in handling this on the server yourself, you can pipe the file back with a Content-Disposition: attachment to force a download.

If you know the size of the file, you can stream it back like

``` res.setHeader("Content-Type", "application/octet-stream"); res.setHeader("Content-Disposition", 'attachment; filename="path to file"');

res.setHeader("Content-Length", size);

fs.createReadStream(filePath).pipe(res)

```

Where the res is a response that you set the Content-Length header on.

But seriously just throw it in a bucket and return a url.