Trying to download file from FTP results in an "500 Illegal PORT command" error

Question

If I execute this locally, everything works fine:

require 'net/ftp'

ftp=Net::FTP.new("myftpserver.com", "username", "password")

ftp.getbinaryfile("/myfile.zip","localfile.zip")
ftp.close

If I attempt to execute it on the Linux server I am using, the result is:

/usr/local/lib/ruby/1.9.1/net/ftp.rb:273:in `getresp': 500 Illegal
PORT command. (Net::FTPPermError)   from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:281:in `voidresp'  from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:304:in `block in voidcmd'  from
/usr/local/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'   from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:302:in `voidcmd'   from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:317:in `sendport'  from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:325:in `makeport'  from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:358:in `transfercmd'   from
/usr/local/lib/ruby/1.9.1/net/ftp.rb:420:in `block (2 levels) in
retrbinary'   from /usr/local/lib/ruby/1.9.1/net/ftp.rb:166:in
`with_binary'   from /usr/local/lib/ruby/1.9.1/net/ftp.rb:419:in `block
in retrbinary'  from /usr/local/lib/ruby/1.9.1/monitor.rb:201:in
`mon_synchronize'   from /usr/local/lib/ruby/1.9.1/net/ftp.rb:418:in
`retrbinary'  from /usr/local/lib/ruby/1.9.1/net/ftp.rb:539:in
`getbinaryfile'

What could be the problem?

Answer 1

I found the answer at http://www.ruby-forum.com/topic/161274:

Beyond firewalls, active ftp won't work behind a NAT device. Ftp servers sometimes say illegal port command if you tell them that your address is a private ip address like 192.168.x (your address on the network behind the nat device)

Adding:

ftp.passive = true

fixed it.