Archive for February, 2009

Using Opentracker – a free, small, fast and powerful tool

Sunday, February 22nd, 2009

What is a tracker in this context? In order to expain that, i need to explain the bittorrent protocoll a little.

Bittorrent as a great and fully legal concept to exchange data. The bad things you hear in the media are cases where people used this concept to exchange data which has copyright on itself.

The principle is quite easy. You install a bittorrent client, download a small file which contains all the necessary data (ending normally .torrent), tell your client to process that information and it will start to transfer files with other people who want or have that file. So if you made your own movie and want to share it, but are short on bandwidth and/or transferlimit you could make a torrent and in the best case have to share the movie once. Then after taking it down, other peers (people who take part in the sharing) will exchange the parts they have and need. So with higher distribution of your file, new leechers (people who download stuff) will face higher availibilty and probably more downspeed.

But how do peers know which others peers have and offer parts? Thats where the tracker joins the game. The tracker is a central point of communcation (its adress is located in the .torrent file, mentioned above) where all clients connect to (via http) and receive information about other clients. There are some so called “open trackers” that allow everybody to announce their files but this article is about the software “opentracker” which allows you to run your own tracker.

In order to get your own tracker you need to download, configure, compile and run the software. All ressources and steps can be found here: opentracker homepage. In short: check out from cvs, edit the Makefile to enable/disable features (for example whitelisting), make, run. You need the libowfat library in order to build opentracker.

Now to run your tracker you need to call the binary. Along can be passed some arguments, that will change its behavior. To tell the tracker to listen on the port 4321 (instead of 6969 by default) and use whitelist.txt as whitelist run:

./opentracker -p 4321 -P 4321 -w whitelist.txt

The file “whitelist.txt” contains the hash of each torrent you want to allow, seperated by a newline.

If you are running your tracker behind a router of firewall, be sure to forward/allow the port you have your tracker listening to.

Opentracker also supports some stats. The URL for stats is

http://trackerdomain:port/stats?mode=

followed by the mode you want to know. It could be: peer, conn, scrp, udp4, busy, torr, fscr, herr, top10, renew, syncs, version, startstop, toraddrem.

This information is taken from ot_http.c at about line 160, look for “static ssize_t http_handle_stats(“. If you want to restrict access to your stats, remove the comment (#) in the Makefile in front of “FEATURES+=-DWANT_RESTRICT_STATS”. Opentracker also supports mrtg for visualisation of statistic data.

To quit opentracker, just kill it (ctrl+c or kill -9 <pid>).

Too bad there is only little to no documentation about this great piece of software. But its so efficient with ressources that even The Pirate Bay uses it for their trackers, and they are the “worlds biggest tracker”.

Kinda like Guitar Hero

Monday, February 16th, 2009

So you know that game where you hit some colored buttons on a plastic guitar and play along kewl songs on the Playstation or Xbox?

The thing is, you need a console for that and it costs money to buy the game and/or the guitar. Solution?

Well, the guys over at JamLegend.com solved that problem by providing a game which only needs your browser (flashbased) and the keyboard. So thats 2 out of 2 requirements pretty much every computer meets today. Im running it within Firefox3 on Windows XP since Flash seems to have problems on my Ubuntu Laptop. And when you have the music lagging behind the keys, its no fun. Believe me!

The principle is simple: you put your fingers around the keyboard like you would around a guitar (no must, do however you like to!), and strum the string with the enter key. Notes are “falling” from the top, and as soon as they pass the field on the buttom, you have to hit them.

There are different difficulties (normal to legendary) and modes (tab and strum), as well as a ranking system, friends community, ability to submit your own songs, duellmode, showdownmode and more to come and all: FOR FREE. If you doubt its something youd like, just play without signing up.

After playing a little with the keyboard i decided i need to have one of those guitars. They are about 40Eur at Amazon. I chose the wireless version since i want to be able to move freely whilst playing a good song. In order to get the xbox controller working on your PC, you need a special receiver (tried bluetooth and WLAN, didnt work) which you can get bundled with a regular controller also at Amazon for again 40Eur. That makes 80 plus some postage, but you can of course sell the controller again.

Once you have everything beside you, you need to install the XBox Windows drivers (should come along on a CD or check Microsoft) and some software to map Joysticksignals to normal keyboard inputs.

I came across Joy2Key, of which you can find a windows-build here. The problem with Joy2Key is, that it cant map the CoolieHat as which the strumming button is recognized. At least i didnt find a way. Thats why i tried JoyCur. Its a tiny program (35kB) that can map every function of the Joystick/Gamepad/Guitar to keyboard strikes. Very good, thanks to that, im ready to map all my keys to play Jamlegend with my Guitar Hero controller. AWESOME!

If you want a standalone program like GuitarHero but cant afford it, check out Frets on Fire. But dont take the newest (1.3.something) version, its full of bugs. Rather look through the forums to find an old stable version and get some songs from there, while you are at it.

Im happy with my setup, i inspired lots of friends already, maybe you’ll have some fun as well!

Here some results, just to show you what it looks and sounds like =)

Canon Rock on Jamlegend.com

Happy Jamming!

PS: Attention! High risk of addiction! Seriously!

Check out: http://www.southparkzone.com/episodes/1113/Guitar-Queer-o.html