Eu estou tentando criar um script para listar e baixar dados de um servidor FTP com Ruby. Eu sou novo no Ruby, então procurei a documentação sobre como usar o Net :: FTP. Eu tenho dificuldade em entender porque isso não funciona:

require 'net/ftp'

server = "ftp.server.com"
user = "myuser"
password = "mypassword"


Net::FTP.open(server, user, password) do |ftp|
        files = ftp.chdir('mydirectory/')
        files = ftp.list
        puts "list out of directory:"
        puts files
end

Isso não funciona, retornando esse erro:

/home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:298:in `getresp': 425 >Failed to establish connection. (Net::FTPTempError)
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:325:in `block in sendcmd'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:323:in `sendcmd'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:402:in `transfercmd'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:478:in `block (2 levels) in retrlines'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:178:in `with_binary'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:477:in `block in retrlines'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:476:in `retrlines'
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:722:in `list'
    from test_ftp.rb:10:in `block in '
    from /home/adhown/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/net/ftp.rb:116:in `open'
    from test_ftp.rb:8:in `'

Alguém pode explicar o que há de errado com o meu roteiro?