When fiddling with Aria2 or various BT download tools, have you seen these kinds of “mini-articles”: “The Most Comprehensive Tracker List of 20XX, Make Your Download Speed Soar!”. Many novice users, overjoyed, frantically paste hundreds of URLs into their configuration files, believing they’ve unlocked the secret to accelerated downloads.
However, looking at the progress bar still only a few KB/s, you might wonder: why, even with so many “servers,” is the download still not moving? In fact, in the modern BT download system, the Tracker’s role is no longer irreplaceable and unique.
Tracker: An Aging “Intermediary”
In the early days of the BT protocol, the Tracker was absolutely central. It was like a centralized information intermediary: when you started downloading, the client would report to the Tracker, “I’m downloading file X, please tell me who has it.” The Tracker would then open its register and give you a list of IP addresses.
However, the Tracker had significant limitations. It is fragile; the supposedly decentralized, anti-fragile peer-to-peer network relies on a centralized intermediary. If the intermediary goes down (server crashes or is blocked), new downloaders can’t find their community. It’s also fragmented; data between different trackers is often incompatible. If you only look at the tracker list, you’re essentially relying on an outdated, centralized search method.
DHT and PEX: Decentralized “Circles of Friends”
To solve the tracker dilemma, modern BitTorrent protocols introduced DHT (Distributed Hash Table) and PEX (User Exchange).
DHT dismantles the intermediary, turning each client participating in the download into a “mini-intermediary.” When you have a resource’s unique identifier (Info Hash), you query nearby nodes. This recursive search snowballs; as long as you can connect to the DHT network, you can eventually uncover users worldwide downloading that resource.
PEX is essentially “referrals from acquaintances.” Once you connect to a peer, they will instantly share the IPs of dozens of other peers they have access to with you.
This is why magnet links can be downloaded without a tracker. As long as you have a hash, DHT can help you build the entire download world.
Why do you still have no speed even though you have a list?
Many users are obsessed with updating their tracker lists, but they overlook something a hundred times more important: network connectivity.
Suppose you are on a large intranet (NAT) and haven’t done port forwarding. This is like having the phone numbers of everyone in the world (the tracker gave you thousands of addresses), but because your home phone can only make outgoing calls, not receive them, those “neighbors” also on the intranet will never be able to initiate a connection to you. In the world of BitTorrent, being visible is more important than knowing where you are.
To address this issue, our Aria2 Manager Enhanced Edition has been deeply optimized. It natively supports automatic port forwarding based on uPnP and is enabled by default. As long as your router supports and has uPnP enabled, Aria2 Manager will automatically create a “green channel” for you on the router, allowing you to instantly switch from a “passive internal network state” to a “proactive public network state,” greatly improving the efficiency of finding peers. (Only applicable to users with a public IPv4 address)
Why are some resources slow on Aria2 but fast on Xunlei?
This is a major complaint from many new users. We need to objectively explain this phenomenon:
Dead Seeds and Unpopular Resources: The essence of BT downloading is “everyone for me, and me for everyone.” If a resource is no longer being uploaded to the entire network (dead seed), or all peers are offline, then Aria2, as a pure BT client, is indeed powerless.
Xunlei’s “Black Technology”: Xunlei is fast because it’s not just a download software; it also has a massive private CDN acceleration server (cloud caching). When you download an unpopular resource, Xunlei may directly extract the data from its own servers and send it to you. Furthermore, Xunlei has a tendency to “leech” data; it acquires data from the BitTorrent network but often prioritizes sending it back to its own Xunlei users rather than feeding it back to the general BitTorrent network. Therefore, Xunlei has evolved from a download tool into a “remote storage + data transmission” service provider, unmatched by ordinary download software.
Giving Aria2 Users the Right Expectations
Using Aria2, you are participating in a fair and open global P2P network.
If you are downloading popular resources (such as the latest Linux images, popular videos): On Aria2 Manager with DHT and uPnP mapping enabled, you will find that the speed can instantly reach full bandwidth, a sense of accomplishment that no centralized software can provide.
If you are downloading extremely obscure and old resources: Please be patient, or be prepared that it may never finish. Aria2 does not have the ability to “create data out of thin air”; it strictly follows the rules of the BitTorrent protocol.
Summary: The Correct Way to Download with Aria2 BitTorrent
To truly make your downloads take off, remember the following:
Keep DHT and PEX enabled: This is the foundation for freeing yourself from tracker dependence (Aria2 Manager has it enabled by default).
Ensure uPnP is working: Check your router settings to ensure uPnP is enabled. Combined with Aria2 Manager’s automatic mapping, you’ll enter a whole new world.
Embrace IPv6: If your broadband supports it, be sure to enable it. IPv6 nodes are usually directly connected to the public internet, significantly increasing the number of peers you can connect to.
Treat Trackers rationally: Keep only 10-20 carefully selected, highly available trackers; leave the rest to DHT.
In the world of BitTorrent, maintaining an “open” connection is far more useful than having a “thick address book.”