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copied!<p>Ok, I have an answer for you but I must warn you that I myself never wrote a bit-torrent client and some answers might not be 100% accurate, all that I wrote is from my understanding of the global view of how bit-torrent work. So I apologize if I wasted your time but I still think you might learn about the core of what you asking about from my answer.</p> <p>•What could be reason of my 80% failed to connect rate? <br/></p> <p>Very complicated to explain in one linear explanation but: - bit torrent ideology is tit-4-tat.. if you're not giving/having tit you ain't getting tat.. UNLESS you just started to download and in that case you might get a "donation" to start with... OR the other side is a dedicated seeding machine.. in that case he might check if you are a giver or just a taker... OR many currently downloading this... OR (fill in your idea..) So, you see there are many, and actually very smart mechanisms to make sure the swarm can be agile and efficient and while some of them can be traced to your machine most of them cannot really be even monitored by your machine least to say under its control.</p> <p>•Do torrent clients send, before closing, a last message to tracker with event=stopped to make it update its internal database with peer info so that it won't send, as a response, a list with useless peer info? Or just they should.. because it really seems I'm receiving dead peers.</p> <ul> <li>It depends on the client code - some might do that some not.. (keep reading)</li> </ul> <p>•Is the order of received peers of any importance? Maybe percentage of completion.. or really random. </p> <ul> <li>It depends on the server code - some might do that some not.. (keep reading)</li> </ul> <p>Alright, Note for those two (keep reading) notes.. You should keep in mind that in a P2P network there is no authority to strictly bind clients or even servers to uphold the protocol to the letter, even if the protocol states something that should be done - it does not mean that every client will implement it or act the same upon it or upon missing it.</p> <p>•Also, every now and then I receive a peer with port 0, which makes my Socket constructor throw an exception. What does port 0 mean? Can I contact it on any port?</p> <ul> <li>Port 0 is kind of a wildcard, if you connect to it - it will automatically connect you to the next available port. (some say next available port above 1023 - but I never tested that)</li> </ul> <p>•Can my PeerId (that I send in Handshake or announce myself to the tracker) influence if the torrent clients I' trying to communicate will continue a started connection? Meaning what if I lie and say that I'm an Azureus client by using '-AZ2060-' as my ID?</p> <p>It will think you are Azureus and if other Azureuses promote connection to Azureuses according to that (and that's a big if there) you will be getting a benefit from it.</p> <p>•Does my piece availability scare off peers? I'm trying to connect, and I send an empty bitfield (I have no pieces, [length: 1][Id = 5][payload: {}]); it seems that they send bitfield, I send bitfield.. (some send like crazy Have messages), they realise I'm poor, they drop me.. some drop connection after handshake. (How rude.)</p> <ul> <li>possible..</li> </ul> <p>•Is there a benefit of not using the classic port interval: 6881 - 6889?</p> <ul> <li>I don't think so - except maybe confusing your ISP..</li> </ul> <p>• Do torrent clients keep internally a list of bad peers (like a black list)? Sometimes after finding a nice peer, I continually used its info in my tests but only 1/3 connection was accepted. Sometimes 10 minutes had to pass to have a successful connection again.</p> <ul> <li>Depends on client Code.</li> </ul> <p>Summary</p> <p>It's a jungle out there - everyone can write its own logic as long as he sending the correct protocol commands - your questions focus on the logical behaviour of clients but there is no common ground as you probably understood by now, this is also the beauty of the bit-torrent and probably the main reason for its success.</p>

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