Simplest HTTP form file uploader.

It just saves uploaded file from HTML form to the new file on the disk.
Also it calculates BLAKE3-256 checksum, replying with it in the answer.

You can upload files with curl:

    curl -F file=@somedata.tar.gpg \
        [ -F comment="optional comment" ] \
        http://localhost:8086/upload/

and verify integrity locally:

    b3sum somedata.tar.gpg

You can enable mail notification with -notify-to and -notify-from options.
It is advisable to run it under daemontools-like supervisor
(http://cr.yp.to/daemontools.html). Example service/uploader provided.

You can also run it as UCSPI-TCP service (https://cr.yp.to/ucspi-tcp.html),
like in service/uploader example.

uploader is free software: see the file COPYING for copying conditions.