LinuxQuestions.org - KTorrent & Azureus Q...

Sadly, there is no easy answer to this. The good news is that I DO have your answers...

IMHO, Ktorrent is a joke. I have never gotten it to run stably or get a decent number of peers connected simultaneously. It is very watered down and inflexible. It's like using a '73 orange hatchback with 4 bald tires and a brown door to get from Overland Park to NYC. I'm sure there are many on LQ who would disagree, and they have good reasons, but I'll let them make those points instead of me (in the interest of brevity).

I personally am a huge fan of Azureus, and so are many others using BitTorrent, according to the info on most of the swarms I get in on.

Here's a little primer:
BitTorrent (the backend software that Azureus/Ktorrent/uTorrent/etc. is actually controlling) not only needs to be able to connect to the tracker to get into the swarm of peers sharing/downloading the file(s) you are after, but the other computers you are connecting to have to be able to find you (unlike most web apps). If you are smart, you are behind either a software or hardware firewall to keep people OUT of your computer when you are on the web. Usually this is a good thing, but for bittorrent to work properly they need to get in.

Crude representation of networking/internet and how it relates to BitTorrent: Imagine the internet or a network as a street. Every desktop, server, web appliance, or whatever is a building on this street. Each of these buildings has doors for going in and out, called ports. With a firewall, most of the doors are locked and the only ones open are the ones you need for surfing the web or retrieving email or whatever you are doing on the network/internet. For BitTorrent to work, ONE of these doors has to be open for the other users in the swarm to get in and get the parts of the torrent you have already downloaded from yet other peers. Your BitTorrent client (Azureus, Ktorrent, whatever) allows you to choose which of these doors it is. Since you are behind a firewall, you have to open the door/port manually. If you don't, you can download, but others in the swarm can't download from you. On the face this sounds good and secure, but because of the nature of BitTorrent such a setup will actually slow you down substantially. It is also extremely rude. For BitTorrent to work you have to give as well as take. If everyone did that, it wouldn't work at all!

Now things get complicated; Azureus is assuming that you are using a home/small office router (actually a NAT box/switch/often an AP all in one tiny box and not a real router, but that is a different debate). What these "routers" do is set THEMSELVES up as the building/computer on the street/internet instead of your PC. Your PC hides behind it and it uses a hardware firewall to keep all of your doors closed from the street, although they may be open to the other computers in your local network, depending on if you are using a software firewall. Once again, this is an excellent security measure, but it is counterproductive to BitTorrent. Whatever port you are telling Azureus/Ktorrent to use needs to be open on your PC AND on the NAT box. Not only that, but the NAT box needs to be told that internet traffic to that port number should be sent to your PC, otherwise it just blocks or silently drops the requests that come in on that port and your PC is unable to upload to the other users in the swarm. Say for example your are using port 13468 for BitTorrent. Once you connect to the tracker and find other users, BitTorrent will tell them that they can connect to port 13468 on your computer to get to the pieces you have already downloaded. They will approach your NAT box on port 13468, which you will have to then FORWARD (important term: PORT FORWARDING) to port 13468 on the computer running BitTorrent. If your computer doesn't have a static address on your local network (a fixed address that never changes), the NAT box can't always forward the traffic, since the address is apt to change.

What you have to do is pick a port (13468 in our example here), go into your NAT box's controls (usually accessed via its gateway address which you can find out via ifconfig) using a web browser, and find a section called PORT FORWARDING. It sometimes goes by other pseudos, but that is the most common one. Tell it to forward all WAN (internet) traffic coming in on port 13468 to the address of your computer on the local network. This is why you need the static IP for your computer. Go to YaST->Network Devices->Network Card and assign your NIC a static address. If your NAT Box (*sigh* router :rolleyes:) uses the address (same as the gateway) 192.168.1.1, you will want 192.168.1.X where X=any number from 2-254 that isn't already in use or used by the DHCP pool. If NAT box=192.168.0.1, then PC should=192.168.0.X. You get the idea. Be sure to set the gateway (192.168.1.1 or whatever), subnet (probably 255.255.255.0), and DNS server(s) (get these from your ISP. They are usually somewhere in the NAT box's interface).

One reason I like Azureus is that it TALKS to you (figuratively). Down at the bottom of the window you will see a little colored dot for your NAT status. If it is gray, it is checking. You probably just started the program. If it is Red with the word "firewalled" next to it, no traffic is getting in. The port is not open in the firewall in the NAT box. If it is yellow and says "NAT reachability problem", the port is open in the NAT box, but communication died there. The port is not forwarded properly. If it is green and says "NAT OK", you are good to go!:cool:

Quick technical comment that I left out in my super-simplified explanation: there are multiple communication protocols that can be used on each port. BitTorrent uses TCP and UDP, so be sure that both are enabled on the port you have forwarded (and opened on your PC if you are using a software firewall). Some NAT boxes (grr... routers) will make you forward the port twice; once for each protocol. My old Linksys box was that way. My current D-Link NAT box allows me to forward both at once.

BitTorrent is VERY taxing on your network/internet bandwidth and can make your internet as slow as a dial-up. Most clients (including Azureus and Ktorrent) will allow you to throttle the upload and download speeds so that your internet connection is still usable for other purposes.

I am a big believer in seeding a torrent for a LONG time. Seeding is when you allow the torrent to continue uploading for other peers in the swarm to access, even though you have already finished downloading it. Each torrent you are tied into has a share ratio. This is the ratio of the amount of data you have downloaded vs. the amount you have uploaded. If you just download until it is finished and then shut things down, you are called a "leech" and don't deserve to be using BitTorrent. Once your ratio has gotten to about 1 or above, most people consider you to have seeded satisfactorily. I personally have a computer dedicated on my network for running BitTorrent/Azureus around the clock and nothing else. That way I can seed my torrents for days/weeks/months without disturbing my other computers. I usually keep a completed torrent available for upload (seeding) until its ratio is >10, then I remove it. I do admit that this is a little extreme, but I have the resources for it and believe in doing my part to make BitTorrent work.

As far as that dumb "search" that Ktorrent has in it: that is just a tiny web browser that is showing you some popular sites for finding torrents. You can get to good sites to find torrents using any browser. My favorites are:
http://www.demonoid.com (requires free registration for some torrents, but worth it. I use an avatar of my daddy on my big lawnmower;))
http://www.isohunt.com
Both sites have plugins to allow searching from the search bar in Firefox and Mozilla/Seamonkey.
There are hundreds of others, but many are really crappy.

Final thought about the inevitable debate I have created in this thread about Ktorrent vs. Azureus: Just because Azureus is complaining and Ktorrent isn't DOES NOT mean that you don't have problems! Ktorrent is just too sissy to tell you about them. Remember what I said about how Azureus TALKS to you? It will also help you solve the problems it finds! Ktorrent just sits there dumbly not working right until it crashes a day or so later and you lose the whole torrent.

WHEW!
That should get you started. Post back with other questions if you need more help.

viel gluck!

J