Not to be confused with UStream, a new technology put together by the folks at BitLet (coverage) called Westream lets you listen to music files that are being distributed via Bittorrent. Up until now there hasn't been an easy way to listen to Bittorrent files without downloading the entire file, or group of files. In the case of Bitlet's system, all you have to do is drop in the URL link to a Bittorrent file, and the system will pull up the tracks, complete with a player that lets you pause, skip songs, and increase and decrease the volume. The one caveat is that the tracks must be in the MP3 or the somewhat less mainstream Ogg Vorbis format; in other words AAC and WMV files need not apply.
One of Bittorrent's strengths is that it goes out and collects pieces of a file as well as it can, while giving some of the smaller, less available chunks the limelight in order to ensure as much of the file is available to seeders as possible. It's a built-in system of self-preservation to make sure the file can continue to be shared even if the amount of people available to share it begin to drop off.
To that end, Westream strikes somewhere in the middle of Bittorrent's file-sharing etiquette, and traditional streaming, simply seeking out the pieces it needs to play the song immediately, while not taking what it doesn't need. While most would consider this a glorified form of leeching, the folks at Bitlet claim otherwise, noting that it "should behave as most torrent clients." The client also uploads whatever it's downloaded into its cache for others, as long as you've got the browser window open.
I managed to get the service to work just fine on several test torrent files, and the music started playing pretty quickly even on torrent files with just a handful of seeders. Your mileage on a home cable or DSL modem may vary, though (we're on a pretty speedy line here at CNET). There were a few hiccups here and there, but it's impressively easy, and requires absolutely no software besides your browser and a recent version of Java.
What really gets me excited about this, beyond the music player is the potential for video. If you're a Web publisher with a video that's got an exceptional amount of people sharing it, this technology takes Bittorrent from being something limited to the tech savvy to anyone who can click a link.
To give the service a spin, check out this (legal) sample torrent running through Bitlet.