Re: FTP Server on Win XP Pro

From: BigAl (bigallanrogers_at_hotmail.com)
Date: 04/30/03 

Date: Wed, 30 Apr 2003 10:12:32 -0700

Thanks for the info Alun. I was wondering, if I put my
ftp server on my router's DMZ, would this solve the
problem? I am using a Linksys WRT54G.

>-----Original Message-----
>In article <008e01c30ee5$88a41460
$3401280a@phx.gbl>, "BigAl"
><bigallanrogers@hotmail.com> wrote:
>>227 Entering Passive Mode (192,168,1,104,5,154).
>>connecting to 192.168.1.104:1434
>>- -
>>connecting to 192.168.1.104:1434
>>Connected to 192.168.1.104 port 1434
>>LIST
>>426 Connection closed; transfer aborted.
>>! Retrieve of folder listing failed (4)
>>
>>Any suggestions? It looks like my computer freaks out=20
>>with the whole passive thing, but if I don't use a=20
>>passive connection in the FTP client, I can't connect
at=20
>>all. Please help! Thanks
>
>This looks like you're running into a problem with your
NAT router. Most
>NAT routers are able to translate the PASV response, so
that it gives an
>external IP and port - but only if they know that you are
running FTP.
>Usually, they decide that you are running FTP by the fact
that you are
>operating the service on port 21, the well-known port for
FTP. In your
>case, however, you're running on a different port, 8181,
and so the NAT has
>no way to tell that this is FTP traffic, and that it
should watch out for
>PASV traffic. Some more expensive and more powerful NATs
have the ability
>to say "treat traffic on port X as if it were FTP", but I
am not aware of
>which particular models do this - most simply assume that
FTP traffic is
>only on port 21.
>
>The key to note here is that the server is behind a NAT,
so PASV is reliant
>on the NAT monitoring FTP traffic for the PASV response.
If the client is
>behind a NAT, too, you'll be reliant on the client's NAT
to modify any PORT
>commands, and that NAT, too, will be likely to not think
the traffic is FTP,
>and therefore not modify the PORT commands. So,
essentially, you're trying
>to do something that isn't likely to work with your
current configuration.
>
>Possible solutions:
>1. Move the server to port 21.
>2. Buy a very expensive NAT router (or, if you have a
very expensive NAT
>router, configure it so that it recognises traffic on
port 8181 as FTP, and
>enables the FTP ALG - Application Level Gateway).
>3. Give the server a public IP address - put it outside
the NAT.
>4. Give the client a public IP address - put it outside
the NAT.
>
>Merely opening the passive ports up, as BB suggested,
will not help, because
>the IP address needs to be translated, and only the NAT
can do that
>correctly. [Try and translate it in the application, as
some FTP servers
>do, and you run the real risk of providing an IP address
and port number
>that the NAT has already assigned to another mapping.]
>
>Alun.
>~~~~
>
>[Please don't email posters, if a Usenet response is
appropriate.]
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