Try out buildtorrent to create a file. Buildtorrent provides Webseed functionality.

To install buildtorrent:

 sudo apt-get install buildtorrent

Usage:

  buildtorrent [OPTIONS] -a http://tracker.yoursite.com input output

  buildtorrent [OPTIONS] -a http://tracker.yoursite.com -f filelist -n name output

To enable Webseed option

--webseeds        -w  <webseeds>   : webseed url list (format: a,b,c)