Saturday, 11 October 2014

P2P throttling and Transmission

Peer to peer technology such as Bittorrent has gotten itself a bit of a bad name, because it is often used to obtain illegal copies of movies, and to otherwise infringe on the intellectual property rights of others. However it is a great way to share large files among a lot of people, and it has plenty of legitimate uses, such as downloading free operating systems and breaking through censorship.
In countries like South Africa, where I live, many ISPs throttle all P2P traffic, especially for uncapped accounts. This means that even if you're paying a small fortune for what first-world countries wouldn't consider an Internet connetion (a 1, 2, or 4 MB line), you may get fairly decent download speeds in most cases, but have all P2P traffic throttled to such an extent that it becomes unusable (many people report speeds as low as 5 KB/s for even well-seeded torrents). One way around this is to download files via P2P to another country, and then direct download from there. Even though you're doing twice as much work, it could well be faster, for unthrottled P2P can be lightning fast, as can a direct download from a dedicated server.
In this post, I look at how to set up a system that allows you to easily do this. We'll be using
  • A Digital Ocean virtual private server (VPS) running Ubuntu-Server 14.10
  • Transmission bit-torrent client (via web interface)
  • vsftpd (very secure FTP daemon)

Transmission

The first step is to install Transmission. This is a cross-platform bit-torrent client, which has an easy to use web interface. These steps are adapted from Daniel Morgan's blog post here.
I'll assume that creating and connecting to the VPS isn't a problem, but see the tutorial here if you need help with that.
Once you're connected to your VPS, run an apt-get update:
sudo apt-get update
Then install Transmission
sudo apt-get install transmission-daemon transmission-common
Now we'll set a username and password to access the web-interface for Transmission. First, we have to stop the transmission daemon, which started automatically when we installed it.
sudo service transmission-daemon stop
Now, edit the config file:
sudo nano /etc/transmission-daemon/settings.json
First, edit the "rpc-bind-address" line, to match the IP address of your VPS. To access the interface from another machine, edit the "rpc-whitelist-enabled" line to false.
Then look for the line that says "rpc-password", and edit the value to a password of your choice. It should look something like the following:
Before your edit:
....
"rpc-password": "{c073045d97f41b82f258e1e204d387f8299a7b22.h73jbg6"
....
After your edit:
....
"rpc-password": "alwaysUseAStrongPassword++^"
....
This password is automatically encrypted, so next time you visit hte file, it'll look similar to the original again.
Optionally, also edit the "rpc-username" field so you can log in with a different username, and if you're worried about using excessive bandwidth on your VPS, set the "ratio-limit-enabled" to true. The default value of 2 ("ratio-limit") means that you'll never upload more than twice the amount of data that you download for any given torrent.
Hit Ctrl + X and then Y to exit and save changes. Once you've done this, restart the transmission daemon with:
sudo service transmission-daemon start
To test that it's working, visit http://123.456.789.123:9091 (where the first part is your droplet's IP address) in your browser. You should see a username/password authentication box. Enter "transmission" and the password you set.
You should now see a web interface. In the top right-hand corner there's an "upload" button, which allows you to upload a torrent file to download. Magnet links also work fine - just paste them into the "or enter a URL" field, and press "upload".
This allows you to download files via P2P onto your VPS. But how do we get them off again. You can use SFTP or WinSCP, etc, where you can log onto your droplet directly via SSH and download files. If you want to download files through your browser too, it's easy to set up an FTP server. Keep in mind that FTP is fairly insecure though.

vsftpd

Installation is as simple as ever:
sudo apt-get install vsftpd
We just need to edit the config file to automatically make available the files that we download through transmission. The default conf file is quite long and full of options, but we'll just move it out the way and use some minimal options.
sudo mv /etc/vsftpd.conf /etc/vsftpd.conf.backup
sudo nano /etc/vsftpd.conf
and paste the following:
listen=YES
local_enable=YES
anonymous_enable=NO
write_enable=NO
local_root=/var/lib/transmission-daemon/downloads/
Then run
sudo service vsftpd
To reload with the new configuration.
Now anything you download via Transmission will be available at: ftp://123.456.789.123/ (again, substitute your IP). When you visit the FTP page, you will be asked for a username and password. You can use any user account on your VPS. If you've only got a root account (a terrible idea, but default on the DO droplets), create a new account:
sudo adduser johnsmith
Enter a new password (twice), and leave the other fields blank when prompted (just press Enter). Now you can use this username and password to access your files.

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I'm far away from home in this country called "Europe". I'm studying towards a Master's in Computational Linguistics (I think - this might help: https://xkcd.com/114/). I write about web applications and Python and other things that you may find interesting (considering you got this far).