From: Felix Windt <fwmailinglists@...>
Date: 2007-10-03T04:58:22+09:00
Subject: Re: Net::POP3 and Firewall

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> -----Original Message-----
> From: Daniel Bye [mailto:ruby@slightlystrange.org] 
> Sent: Tuesday, October 02, 2007 11:18 AM
> To: ruby-talk ML
> Subject: Re: Net::POP3 and Firewall
> 
> On Wed, Oct 03, 2007 at 02:50:19AM +0900, Mike Ho wrote:
> > This code woks on my home PC - i.e. no firewall. Does 
> anyone know what's 
> > needed for it to run from behind a firewall?
> > ###############
> > require 'net/pop'
> > 
> > 
> > pop = Net::POP3.new('pop.mail.yahoo.co.uk', 110, false)
> >     pop.start('myUserName', 'myPwd')
> >     if pop.mails.empty?
> >       puts 'No mail.'
> >     else
> >       i = 0
> >       pop.each_mail do |m|
> >         File.open("inbox/#{i}", 'w') do |f|
> > 
> >           f.write m.pop
> >         end
> > 
> > 
> >         i += 1
> >       end
> >       puts "#{pop.mails.size} mails popped."
> >     end
> >     pop.finish
> > 
> > #################
> > 
> > I'd really appreciate any thoughts or comments.
> 
> I don't know of any programmatic way to do this - have you 
> spoken to your
> firewall administrator? He will need to allow POP3 traffic out to the 
> Internet (at least from the box hosting your app to the POP3 
> server it is
> trying to contact) and back again.
> 
> You could also check out SOCKS, which may enable you to proxy through
> the firewall.
> 
> Dan
> 
> -- 
> Daniel Bye
>                                                                      _
>                                               ASCII ribbon 
> campaign ( )
>                                          - against HTML, vCards and  X
>                                 - proprietary attachments in 
> e-mail / \
> 

One faily cheap and easy trick - if the requirements are met - is tunneling
over SSH. If the firewall allows SSH traffic to the internet, and if you
have a machine outside the firewall that you can SSH to, you can 'proxy'
your POP3 like so:

ssh -L5000:ip.of.mail.server:110 user@ip.of.ssh.server

And then connect to localhost:5000 to retrieve mail.

You could probably also utilize net/ssh as a ruby library to build the
tunnel within the script, though I've never done that.

If this is in a corporate (or other network policy) situation, note that
_any_ circumvention of the firewall will be very, very frowned upon and may
lead to termination - always check with the policy makers first.

HTH,

Felix

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