Free bittorrent software for linux

Transmission is a free BitTorrent client written from scratch in C. Transmission is still in early development stage.
Transmission aims to be as efficient as possible. Transmission runs on Mac OS X, BeOS, Linux and NetBSD (and probably on other UNIX-like systems too). Only the Mac OS X version has a graphical interface yet.
Transmission is released under the MIT license.
Enhancements:
- Fix 0.80 assertion crashes
- Fix a bug that miscounted how many peers Transmission wants connected
- Correct incorrect error messages
- Memory leaks fixed

Linkage is a Gtk+ BitTorrent client written in C++.

Linkage is a BitTorrent using gtkmm and libtorrent. Features include DHT, PEX, UPnP, desktop notifications and torrent creation.

CTorrent_ipv6 is a BitTorrent Client program written in C/C++ for Linux and FreeBSD. Fast and small are CTorrent_ipv6s two strengths.

The application works only with new internet protocol called IPv6 or IPng.

Generic Options:

-h/-H Show this message.
-x Decode metainfo(torrent) file only, dont download.
-c Check exist only. dont download.

Download Options:

-e int Exit while seed hours later. (default 72 hours)
-p port Listen port. (default 2706 -> 2106)
-s save_as Save file/directory/metainfo as...
-C cache_size Cache size,unit MB. (default 16MB)
-f Force seed mode. skip hash check at startup.
-b bf_filename Bit field filename. (use it carefully)
-M max_peers Max peers count.
-m min_peers Min peers count.
-B rate Max bandwidth (unit KB/s)
-P peer_id Set Peer ID [-C61304-]

How to install:

$ ./configure
$ make install
$ hash
$ ctorrent_ipv6 -h

BitTorrent is a FREE software for copying files from one machine to another. FTP punishes sites for being popular.

Since all uploading is done from one place, a popular site needs big iron and big bandwidth.

With BitTorrent, clients automatically mirror files they download, making the publishers burden almost nothing.

qBittorrent is a bittorrent client written in C++ / Qt4 using the good libtorrent library (By Arvid Nordberg).
qBittorrent aims to be a good alternative to all other bittorrent clients. The Author is Christophe Dumez, French Student in computer science (IT).
Main features:
- Fast resume of unfinished downloads on startup (no need to recheck files)
- Unicode Support
- Connection through proxy server support
- Download only some files within a torrent
- Scan regularily a folder and add automatically torrent files within to download list
- Drag n drop of torrent files to GUI
- Limit Upload / Download Speed
- Limit number of simultaneous connections
- User can set share ratio
- UDP Tracker support
- IP Filter support
- Display number of peers, complete / partial sources for each download
- Languages supported: English, French, Simplified Chinese, Spanish, Korean, German, Catalan, Polish, Dutch, Turkish, Greek, Russian, Swedish

LibTorrent is a BitTorrent library written in C++ for Unix. LibTorrent library is designed to avoid the redundant buffers and data copying that most (all?) other BitTorrent implementations suffer from.
The library is single-threaded and the client handles the select loop. An interactive ncurses client is included as an example.
Main features:
- The client has full control over the polling of sockets.
- Sigc++ signals makes i easy for the client to react to events.
- Fast resume which checks the file modification time.
Direct reading and writing from network to mmaped files:
- Avoids duplication of data where both the application and the kernel has a copy of the file chunk.
- Unused chunks get thrown out or written to disk instead of the swap.
- Kernel handles caching of the file.
File hash check:
- Uses the same thread.
- Client can control the rate. (Will be improved)
- Non-blocking and preload to memory with the mincore and madvise system calls.
File handler:
- Fine-grained use of file read/write permissions, allows seeding of read-only files.
- Allows torrents with unlimited number of files.
- Opens closed files when mapping chunks to memory, with graceful error handling.
- Support for files larger than 2 GB.
- Different download priorities for files in the torrent.
- Multi-tracker support.
- No dependency on any specific HTTP library, the client implements a wrapper class.
- Dynamic request pipe size.
- Upload and download throttle.
- And much more i havent bothered mentioning. (nor implementing)