Best port for torrenting

The problem with most P2P networks is that many people just don’t like to share. They open up their program, download their files, then close the program before they can help anyone else. It’s called leeching. Behavioral judgements aside, if everyone did this then nothing would ever get shared! To combat this, BitTorrent has gone back to the way of sharing you were probably taught as a young child: trading. Instead of waiting for the complete file to download before it starts to share, BitTorrent downloads the file in small pieces and shares each piece as it finishes. This makes it easier to get the file from many different people at once, thereby increasing the probably that you’ll get a good download speed. It also means that downloading a file is more reliable than in some other networks. If Charlie has half of a file and Bob has the other half, Alice can get each half and put them together to get the whole file. Spiff, eh?

Purpose

Far too many people new to BitTorrent just install the client and expect everything to magically work. Then they connect to a torrent that has a ton of seeds, they get a horrible download rate and a high upload rate, and they think BitTorrent sucks. What they don’t know is that their problems are almost certainly due to misconfiguration of their systems and a lack of understanding of how BitTorrent (and other p2p sharing) works. The purpose of this document is to educate you, the reader, and hopefully help you tweak your system to get the most out of BitTorrent.

How BitTorrent Works (and most other P2P sharing networks, too)

Basic Networking: IP Addresses and Port Numbers

I’m going to give a rudimentary explanation of networking as I go through this, in an attempt to make sure I don’t go over anyone’s head. Feel free to skip this section if you already know this stuff.

When your computer connects to the Internet (whether via dialup, DSL, cable modem, or whatever), it has to have a unique identifier associate with it, so that all of the other computers on the Internet can talk to it. (Kindof like a driver’s license number, or a Social Security number, or even a telephone number.) This identifier is called an IP address. Since computers work best with numbers, an IP address is actually just a really big number. When your computer wants to download something like a file or a web page (or upload, for that matter) it figures out what the IP address is for the computer you are talking to, and it tells the computers around it that it wants to talk to the target computer. Kindof like the old game of telephone, the message eventually gets to the target computer and it talks back to your computer in the same manner.

Since computers can talk to many different computers at once, and can talk about a variety of different things (web pages, file sharing, video downloading, real time audio, etc.), they have to have a way of differentiating which conversations are about what. Again with the numbers, computers on the Internet group all related things by giving them the same port number. For example, web pages tend to be on port 80, secure web pages are on port 443, programs from companies for download (like shareware) tend to be on 21, and so on. It is the combination of the IP address and the port number that makes the conversation between two computers happen.

Basic Filesharing: Client-Server and P2P

Again, skip ahead if you know this part. I won’t be offended.

A few years ago the Internet was pretty easily divided into two groups: servers and clients. (Just like at a restaurant.) There weren’t that many servers, but their primary job was to hold web pages and files to be downloaded. They didn’t do much other than sit there and wait for people like you to request a web page or file. You, as the client, probably didn’t share any files or web pages with anyone. This segregation was primarily due to the fact that it takes a lot of outgoing bandwidth to share stuff. In a time before broadband DSL and cable modems, back in the days of dialup, most people didn’t have the bandwidth, let alone the knowhow to share stuff on their own. This old system was called client-server, appropriately enough, and it is still used today for the vast majority of stuff on the Internet, including web pages.

With the advent of broadband technologies such as DSL and cable modems, the everyday user like yourself suddenly has a big chunk of bandwidth, not only for download, but also upload. Sharing files directly from your computer (without first sending them to a server) is now a reality. This is where p2p comes in. The acronym p2p stands for peer-to-peer, which basically means client to client. That is, you download files from people like you instead of from big servers, and in turn they download files from you. You share your files, your friends share their files, and everyone talks directly to each other.

Basic P2P

We’ll use three people to demonstrate the concepts here: Alice, Bob, and Charlie. For all of the examples, we assume that Alice is a total newbie and has just installed her first p2p software, has nothing to share, and is looking to download something. Bob is sharing a few things, but is also looking for more stuff to download. Charlie is sharing a bunch of stuff but doesn’t spend much of his time looking for new stuff to download.

For pretty much all p2p systems most people follow these basic steps:

1. Search for something
2. Get a list of everyone who is sharing what they want
3. Go through the list and ask each person on it if they will please send the file
4. Once the file is complete, start sharing it with other people in the system

So, Alice searches for Matrix Reloaded, finds out that both Charlie and Bob have it, and asks both of them to please send her the file. If they aren’t too busy helping other people, hopefully they’ll be able to help her out. Once she has the file, she starts sharing it as well, so that other people can get it.

BitTorrent follows this progression closely, with a few differences. In many systems (such as Napster, KaZaA, or eDonkey) searching for a file is built right into the program. BitTorrent isn’t meant to be a full-blown network like they are, and so it doesn’t have this feature built-in. You have to find the torrents yourself, probably with Google or some other popular search engine. The other difference is in the way sharing works.

Basic BitTorrent Sharing

The problem with most P2P networks is that many people just don’t like to share. They open up their program, download their files, then close the program before they can help anyone else. It’s called leeching. Behavioral judgements aside, if everyone did this then nothing would ever get shared! To combat this, BitTorrent has gone back to the way of sharing you were probably taught as a young child: trading. Instead of waiting for the complete file to download before it starts to share, BitTorrent downloads the file in small pieces and shares each piece as it finishes. This makes it easier to get the file from many different people at once, thereby increasing the probably that you’ll get a good download speed. It also means that downloading a file is more reliable than in some other networks. If Charlie has half of a file and Bob has the other half, Alice can get each half and put them together to get the whole file. Spiff, eh?

But this piecewise downloading doesn’t necessarily combat the leech problem. As a backup plan, BitTorrent built in the other half of trading you probably learned as a kid: tit-for-tat. That is, if you give me one piece, I’ll give you one piece back. BitTorrent will give you a few pieces of the file for free to help you get started, but after that you need to start giving some pieces back if you want to keep downloading. If you don’t share, eventually everyone else will stop talking to you. Just like when you were a kid with your toys on the playground. In fact, BitTorrent goes one step futher and actually starts to favor the people who share the most. This means that the more you upload, the faster you’ll download.

For example, Alice gets a few pieces of a file from Bob for free. She can then give those pieces to Charlie, if he doesn’t already have them, which will motivate Charlie to return the favor and give her a bunch of pieces that she doesn’t have. She then goes back to Bob with those pieces, and the cycle continues and grows. Why don’t Bob and Charlie talk directly? Maybe they do but they haven’t gotten to those pieces yet. Or maybe their systems aren’t configured right and they can’t talk directly to each other.

How does all this start? With BitTorrent, it starts with a tracker. Like the name suggests, a tracker keeps track of people who are interested in torrents. When you download a .torrent file it contains a link to a tracker as well as an identifier (hash) which is unique to that specific torrent. Your BitTorrent client then connects to the tracker and asks for a list of all people interested in that torrent. At the same time, the tracker adds you to that list so that other people know that you are interested. Your BitTorrent client will also periodically asks the tracker for an updated list. That’s all a tracker does: keep track of that list for each torrent, and give it out to people who are interested. The tracker does not know anything else about the torrent, nor does it send you the file. It just shows you where to go to get the file. (Like an Information Booth at a mall.)

Firewalls

This is where things get hairy. In all likelihood, you may be behind a firewall. Many people are. A firewall is like a personal bodyguard for the Internet. You talk to your firewall, and your firewall talks to the Internet for you. That way, you don’t have to talk to the Internet directly, and any bad people on the Internet can’t bug you. By their very nature, firewalls are paranoid and untrusting things. For the most part, a firewall won’t let anyone talk to your computer unless you tell it to let them, and telling it to let them is tricky. Since most firewalls assume that if you talk to another computer then that computer is allowed to talk back to you, many P2P networks will try both methods.

Let’s assume that both Bob and Charlie are behind firewalls, while Alice is not. Alice cannot start a private conversation with either of them, as she can’t get past their firewalls. Both Charlie and Bob can easily start a conversation with Alice. However, Bob and Charlie can’t talk to each other because they are both behind firewalls and neither can start the conversation. Like so:

NAT and Port Forwarding

But wait, it gets worse! In addition to being behind a firewall, your firewall probably performs something called Network Address Translation, or NAT for short. (Some geeks also call it masq, but the rest of the world calls it NAT.) Remember how having your IP address is the key to other computers talking to you? An extra layer of paranoia and security is to have your firewall give you a fake IP address so that even if they wanted to people couldn’t talk directly to you. Like having a phone number that starts with 555-. You start a conversation with someone else, your firewall intercepts it and actually starts the conversation for you, and the computer on the other end talks with your firewall as if it were you. In fact, the computer probably can’t tell the difference between you and your firewall. The problem is that your computer probably only knows about this fake IP address, so when it talks to the tracker and tells the tracker to add it to the list, it gives the tracker the wrong IP address. When the tracker gives out that fake IP address to someone else and they try to connect to you to give you some of the file you want, they can’t find you because your IP address is bogus. So instead of giving out your fake IP address to the rest of the world, you need to give them an IP address that they can actually talk to: the IP address for your firewall.

One more hurdle to go. Remember how firewalls don’t normally let other people start talking to you without you talking to them first? Even if you give out your firewall’s IP address to everyone else, when they try to start a conversation with your firewall it will just ignore them, as it doesn’t know what they want and it doesn’t trust anyone. Logically then, you need to explain to your firewall that in some instances it is okay for people to start conversations with you. This is where those port numbers come back in. The port number that the other computers use to describe the conversation they are starting will let the firewall know what they are talking about. The firewall can then check and see if that port number matches something you want people to come directly to you for, and it will let them start talking to you. Since your firewall is forwarding on the conversation to you, this is called port forwarding.

Once you get the bogus IP address issue and the port forwarding straightened out, people will be able to talk to you. Let’s say that Charlie, being such a hip and knowledgeable guy, has this all set up. Bob, on the other hand, hasn’t figured it out yet and is still setup incorrectly. This means that now Alice and Bob can start talking directly to Charlie, but neither Alice nor Charlie can start conversations with Bob. Like so:

But what does it all mean.

Look at the diagram above. Remember how BitTorrent requires you to trade pieces in order to get good download speeds? If Alice and Charlie can’t upload pieces to Bob, Bob will eventually start ignoring them. When that happens, Bob loses out because they’ll start ignoring him back. Everybody loses. Since Alice and Charlie can converse freely, they are going to probably get good download rates from each other. In other words, the more people that can talk to you, the better your speeds are going to be. Configuring your firewall and BitTorrent client correctly is therefore essential for getting good download speeds!

Firewall Configuration

Forward the BitTorrent Ports To Your Computer

Most hardware firewalls (such as firewall routers) have the capability for port forwarding. If you are running a software firewall (such a ZoneAlarm or BlackIce), then portforwarding is probably called something else, like “Application Internet Permissions” or somesuch. The BitTorrent client will normally use ports 6881 to 6889, so when you are adding the ports to your firewall, make sure you cover the whole block. Many newer BitTorrent clients have larger or changeable port ranges, so check with the instructions for your client software first. For most of these instructions you will need to know what your computer’s IP address is. Under Windows NT, 200, and XP, go to Start >> Run >> type cmd and click OK >> at the prompt type ipconfig and press Enter. Under Windows 95, 98, or Me, go to Start >> Run >> type winipcfg and press Enter.

Linksys Firewall Router

Access your Linksys Firewall Router’s web admin page, according to the instructions in the manual for your router. You will probably need to enter a password. At the top of the web page there is a series of navigational links, and you want the one that says “Advanced”. From there, move on to “Forwarding”. Find an empty row in the form on that page, and fill in the name (“BitTorrent”), the port range (6881 to 6889), check the TCP box, and set the IP address to the one that your computer is. Check the Enable box then click the Apply button to save the changes.

Netgear RT 314 (and possibly other models)

From Pezko Stenmark:

Access the web administration interface. Then click Advanced in the menu to the left, then click Ports. Use an empty row (everything is zero) and enter in the first column (“Start Port”) 6881, in the second column, enter 6889, and the last one, enter the IP address for the computer running BitTorrent. Click the Apply button, and you’re done

Netgear RP114

From Adam Johnston:

1. Under Windows NT, 200, and XP, go to Start >> Run >> type cmd and click OK >> at the prompt type ipconfig and press Enter. Under Windows 95, 98, or Me, go to Start >> Run >> type winipcfg and press Enter.
2. ‘IP Address’ is the address of your PC, ‘Default Gateway’ is the IP address of the router
3. In Internet Explorer (or another browser) type the IP address of the router into the address bar.
4. Enter in your name and password. (Defaults are ‘Admin’ and ‘1234’)
5. Go to ‘Advanced’ >> ‘Ports’
6. In the “Start Port” and “End Port” fields enter the port range (6881 to 6889), and in the “Server IP Address field” enter in the IP address of your PC. Apply.

USR Broadband Router

From Andy Haninger:

On the USR router, it’s an option in the web-based config tool. The option is called “Virtual Server” and you enter the port and the IP of the virtual server for it to forward. (The computer running BitTorrent.)

Linux IPTables

iptables -t nat -I PREROUTING -p tcp –dport 6881:6889 -j DNAT –to-destination
. where is the private or internal IP actually running the BT client.

Shorewall for Linux

For systems that are using masquerading (NAT) and have something like the following:

In /etc/shorewall/masq :

# All outgoing traffic from 192.168.1.X going out the eth0 interface
# will be NATed/masqueraded to appear to be originating from your external
# internet address A.B.C.D (i.e. SNAT outgoing packets)
eth0 192.168.1.0/24 A.B.C.D

And in /etc/shorewall/rules :

# Allow net zone traffic on the external interface to be destination NATed (DNAT)
# to your computer’s internal IP address (for example, 192.168.1.X)
# Allow BitTorrent traffic through – port 6969 is if you run a tracker
# And ports 6881 through 6889 are for incoming BitTorrent connections.
DNAT net loc:192.168.1.X tcp 6969
DNAT net loc:192.168.1.X tcp 6881:6889

Linux ipmasqadm

From Andy Haninger:

ipmasqadm portfw -f (flushes all other rules.. optional)
ipmasqadm portfw -a -P tcp -L [firewall IP] 6881 -R [client IP] 6881

Other Firewalls

I’ll try to add new firewall configuration instructions here as I go. If you have a firewall and can type up clear instructions that you think will help others, please email them to me at the address provided in the Version Information section of this page.

BitTorrent Client Configuration

Setting Your External IP Address Correctly

This is actually pretty tricky. Every time you disconnect and reconnect to the Internet, you have a good chance of getting a different IP address. If you are a dialup modem user, it’s pretty much a guarantee. Broadband cable and DSL users get new addresses somewhat infrequently, since they are always online. (You probably only get a new one when your service provider is doing network maintenance.) If you are behind a firewall, it probably handles all that for you without you having to worry about it. However, if you are going to set your BitTorrent client up to tell the tracker the correct IP address, you need to know what it is. The easiest way is to go to a web site which will tell you, and a search for “check IP address” will probably turn up a few (checkip.dyndns.org, whatismyipaddress.com, bnl.gov, dnsart.com). The official BitTorrent clients all support a commandline option to tell them what your IP address is ( –ip 1.2.3.4 ) so just substitute in your IP address and you are good to go. If you start getting weird errors from the tracker, or you can’t seem to download anything, your IP address may have changed and you may need to update the BitTorrent commandline options. Yes, it sucks to have to do this manually, but it really does help. Your BitTorrent commandline will then probably look something like this:

“c:\program files\bittorrent\btdownloadgui.exe” –ip 123.45.67.89 –responsefile “%1”

This step may be unnecessary, depending on how smart the tracker you are talking to is. You should try the port forwarding instructions in the previous section first, and then do this if it doesn’t seem to work.

History

The BitTorrent client that runs Deliver8r’s Alias site has been set to only send data to people that it can connect directly to. People who are incorrectly configured (behind a firewall without port forwarding) can still join the swarm and download from other clients, but since the primary seeding client won’t talk to them they are at a serious disadvantage. If a torrent is out of seeds and they can’t talk to the primary seeding client, odds are they will never get the file they want. Hopefully, this document has helped anyone suffering from this problem to resolve their issues by correctly configuring their system. This probably wasn’t the first site to go to such a system, and it probably won’t be the last. Configure your system correctly now and save yourself future headaches.

Further Reading

• How BitTorrent Works, 101
• Official BitTorrent FAQ

BitTorrent

BitTorrent is a protocol designed for transferring files. It is peer-to-peer in nature, as users connect to each other directly to send and receive portions of the file. However, there is a central server (called a tracker) which coordinates the action of all such peers. The tracker only manages connections, it does not have any knowledge of the contents of the files being distributed, and therefore a large number of users can be supported with relatively limited tracker bandwidth.

A recent extension to BitTorrent is the DHT (“distributed sloppy hash table” or simply called UDP tracker) protocol. A UDP based peer to peer tracker protocol. And the uTorrent imports another UDP based Micro Transport Protocol, called uTP.

History

In April 2001 Bram Cohen designed the BitTorrent protocol, which he implemented summer 2002. The first program to use the protocol was the original BitTorrent client. Today many applications are availiable, and the protocol is widely used.

Protocol dependencies

• TCP: Typically, BitTorrent uses TCP as its transport protocol. The well known TCP port for BitTorrent traffic is 6881-6889 (and 6969 for the tracker port). The DHT extension (peer2peer tracker) uses various UDP ports negotiated by the peers.

Example traffic

XXX – Add example traffic here (as plain text or Wireshark screenshot).

Wireshark

The BitTorrent dissector is (fully functional, partially functional, not existing, … whatever the current state is). The DHT extension has been supported since r39653. The uTP extension has been supported since r36716.

Preference Settings

• Reassemble BitTorrent messages spanning multiple TCP segments
• Decode the peer_id of the handshake messages

Example capture files

SampleCaptures/BitTorrent.Transfer1.cap (Microsoft Network Monitor) Here’s a capture with a few BitTorrent packets; it contains some small packets I got whilst downloading something on BitTorrent.

SampleCaptures/BITTORRENT.pcap (libpcap) Capture file of two torrent clients communicationg without DHT or peer exch.

Display Filter

A complete list of BitTorrent display filter fields can be found in the display filter reference

Show only the BitTorrent based traffic:

 bittorrent

Note: implemented in Wireshark post 0.10.12!

Capture Filter

You cannot directly filter BitTorrent protocols while capturing. However, if you know the TCP port used (see above), you can filter on that one.

Capture only the BitTorrent tracker traffic over one of the default ports (e.g. 6881):

 tcp port 6881

Capture the BitTorrent tracker traffic over the range of default ports (e.g. 6881-6889):

 tcp portrange 6881-6889

when using libpcap 0.9.1 or later or WinPcap 3.1 or later; that expression won’t work with older versions of libpcap or WinPcap, so, on Windows, upgrade to WinPcap 3.1 or later and, on UN*X, upgrade to libpcap 0.9.x if possible and, if not possible and you have a version of libpcap prior to 0.8.1, use

 (tcp[0:2] >= 6881 and tcp[0:2] = 6881 and tcp[2:2] 

(a bug in the libpcap optimizer in libpcap 0.8.x means this won't work with libpcap 0.8.x, although you might be able to use tcpdump with the "-O" flag).

External links

• http://www.bittorrent.com/ the official BitTorrent page
• Wikipedia Bittorrent page
• How BitTorrent Works about P2P in general, BitTorrent and firewall settings
• DHT Protocol (BEP 5), the UDP-based BitTorrent extension for distributed trackers (the UDP port number is negotiated). Also: link to draft DHT protocol (dead link), Web Archive Copy (2007-12-21) of draft DHT protocol.
• Hippie protocol signature description the TCP and UDP protocol signatures which might be used to heuristically identify the BitTorrent protocol Web Archive Link
• More on BitTorrent

How To Open Ports For Your Torrent Client

Depending on which torrent client you use, the process for opening ports will be different. We’ll go over the process for two of the most popular torrent clients: uTorrent and qBittorrent.
If you’re not sure which ports to open for your torrent client, the best thing to do is open all the ports in the range 6881-6889. That’s the default port range that most torrent clients use.
To open ports in uTorrent, go to Menu > Options > Preferences. Then, click on the “Connection” tab and make sure that the “Randomize port each time utorrent starts” box is unchecked. After that, enter the port range that you want to use in the “Port used for incoming connections” field.
To open ports in qBittorrent, go to Menu > Tools > Options. Then, click on the “Connection” tab and make sure that the “Randomize port each time qBittorrent starts” box is unchecked.
Once you’ve opened the correct ports in your torrent client, you’ll need to forward those ports through your router. The process for doing that will vary depending on which router you have. You can usually find instructions for how to do that by searching for your router’s model number and “port forwarding.”
After you’ve opened the correct ports and forwarded them through your router, your torrent client should be able to connect to other clients and start downloading files.

uTorrent can be run on any port with a port above 10000. You can change the input port of your uTorrent from 10000 to 65535 by using the output random port feature. It can be executed in 30 seconds or less without port forwarding (leaving a passive node). Port numbers will not change regardless of which time the file is downloaded. Although antivirus software may affect alternative torrent clients, torrent sites are unaffected. A basic TCP port (6989 for tracker traffic and 6881-6889 for torrent traffic) is required. If you want to configure UPnP on your uTorrent / routers, you should contact them.

Using TCP and UDP, Bittorrent searches files and transfers them. If you can’t get to the default TCP ports of 6881-6889, 6969, or 8080, you’ll need to use port 80. Some bittorrent clients also support HTTP downloads. To completely block BT, you must use UDP port 1024-553-6 in your router.

Which Port Is Best For Torrent?

Credit: BetaNews

The TCP port recommended and possibly the best for torrenting is 6881-6889. As a result, if you’re still having trouble downloading torrent files quickly, you can try installing the program on your computer.

Does Utorrent Use Udp Or Tcp?

A trace shows uTorrent uses both TCP and UTP, depending on the protocol switching in the middle of the download.

What Is The Best Port To Use In Qbittorrent?

If you’re using a port between the 49160 and 65534 ranges, go with it. Because the old port range by torrent programs was typically 6881-6999, many ISPs began blocking that specific range of ports.

What Ports Need To Be Open For Bittorrent?

Credit: Lifewire

It is normal for BitTorrent clients to use ports 6881 to 6889, so make sure you cover the entire block when adding those ports to your firewall. Because many newer BitTorrent clients have larger or even variable port ranges, make sure your client software has the appropriate instructions.

When you connect your computer to the Internet via port 58261, your BitTorrent client will communicate with other BitTorrent clients. To ensure the best download rates, you must use this port. Although most PCs are unlikely to block non-standard ports as part of the standard operating procedure, it is a good idea to do so in this case. Your router can connect you to the Ten Foot BitTorrent Client. You can use port forwarding to connect a PC to another computer. Because of a bug in the Microsoft UPnP library, some clients may display an UPnP error message. If it doesn’t work, we provide workaround options.

What Ports Do You Need To Open For Bittorrent?

Table 1: Ports that must be opened for bittorrent communication. This port can be used to send the message *br This packet was sent via TCP 22 / br. br> BitTorrent (*br>). TCP 23 is a class of protocols. In Brazil, there is a Telnet. #DIOPT 161: *br [br]GET abr[/br]
SNMP trap. Because most BitTorrent clients use random high ports that aren’t intended for other services, port forwarding of any five-digit port number is unlikely to be a risk to the client. You must, however, perform a test run first to ensure that all of your devices can communicate using the new port number before you can enable port forwarding.

What Ports Do Utorrent Use?

The standard range of BitTorrent TCP ports is 6881-5889. Despite this, the protocol is capable of running in almost any port number, making it difficult to block. If you don’t want to use a random number, you should provide a port number greater than 10000 (as stated above).

Utorrent Routers

There are many different types of utorrent routers on the market. Some are designed for specific types of networks, while others are more general purpose. The best router for your needs depends on the type of network you have, the number of devices you need to connect, and the level of security you require.