Over the line

Connect to Transmission through an ssh encrypted session

~2 min read in opensource

Use case: You have a remote machine with high bandwidth and you want to turn it in a torrent server.

Prerequisites

All you have to install in the remote server, is transmission-daemon which is pretty much included in every well known distribution. After it successfuly installs, run transmission-daemon as your user, no need for extra privileges. See the man page for extra commands.

In the client side you will need Transmission Remote Gui (I will call it transgui from now on), a cool cross platform front-end to remotely control a Transmission Bit-Torrent client daemon via its RPC protocol. In Fedora you can install it from the official repos with:

yum install transgui

whereas in Archlinux you can find it in AUR. I suggest you go with the bin one which is a precompiled binary so that you avoid the building time.

Now, there is this little bash script which makes an ssh connection to you server, in order to link transgui with transmission-daemon:

#!/bin/bash

RPORT=9091
LPORT=9092

ssh -C -c blowfish -f remotevm -L $LPORT:localhost:$RPORT -N

if [ 'x'$1 == 'x' ];
  then
    echo "Connection established"
  else
    echo "Connection failed"
fi

Let's cut it down to pieces.

  • -C is optional and it will compress all the data of the session. As the man page dictates, use it only on slow connections (client side).
  • -c blowfish selects the cipher specification for encrypting the session, in this case blowfish.
  • -f requests ssh to go to the background.
  • remotevm is just an alias of the remote server I have at my ~/.ssh/config in which I use an ssh key to connect to, without using a password.
  • -L $LPORT:localhost:$RPORT specifies that the given port on the local (client) host is to be forwarded to the given host on the remote side. Here I use RPORT for the remote side and LPORT for the local one. Note that 9091 is used by default from transmission as its bind port. All this is traversed through localhost, no external IPs.
  • -N makes sure there isn't executed a remote command. This is useful for just forwarding ports.

Transgui

After you run the above script and see the Connection established message, it's time to open transgui and connect to the remote server. Make a new connection as it appears in the image below.

Connect to transgui

Default username:password is transmission. If you want to change it, either pass it as a parameter when running transmission-daemon (see man page) or edit $HOME/.config/transmission-daemon/settings.json with the daemon stopped.

Some more screens:

Download dialog The dialog that appears when you open a torrent file

Downloading Fedora Main download page

Now all that remains is to retrieve the downloaded data. There are numerous ways to do so, like using scp, rync, ftp, sftp, sshfs etc, each serving its own purpose.

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