Update 2017: The only working method is now to use Vuze’s Swarm Merging starting the two torrents at the same time. Vuze will auto-detect the uncompleted torrent files merging the two toghether. Remove .part extension of existing files if you put uncompleted files from another client.
Update October, 2010: before trying this howto, I suggest to try mergetorrent. It’s free software, released under GNU GPL by Eyal (read comments) and it’s simpler than the method described below. Thank you Eyal!
Sometimes you want to download a torrent that you’ve partially downloaded. Many bittorrent client allow partially downloaded files, but what if you’ve downloaded the same torrent twice, with differents parts available?
Use Zeroconf / Local peer
I’ve used two client on the same LAN, ktorrent (on Debian) and utorrent (on Windows XP). I’ve two downloaded files (or folder) from the same .torrent, with different parts downloaded.
- Enable Zeroconf plugin on ktorrent
- Check if on utorrent “Enable local peer discovery” is enabled
- Import existing download #1 on ktorrent
- On debian system, as root type ifconfig to discover your local IP address, i.e. inet addr:192.168.0.XX
- Go to ktorrent preferences and check the used port (e.g. 12345)
- On utorrent go to Peers tab on #2 download. Right-click > Add peer
- Type your first machine IP address (e.g. Debian) and the first bittorrent client port (e.g. 12345 on ktorrent), e.g. 192.168.0.XX:12345 with no protocol prepended.
On both client you’ll notice a new peer, downloading and uploading very fast. Little after, the two downloaded files / folder could be completely merged.
You can now close #2 and continue to download the torrent on a single machine / client from external peers.
Note: I’ve tested this method on the same machine using Virtualbox (Debian as host, XP as guest).