Re: FTP-Data connections?

[Mikael Olsson <mikael.olsson () enternet se>]

Fernando,

fernando_montenegro () hp com wrote:
> When connecting to a remote FTP server (I've tried ftp.microsoft.com,
> ftp.redhat.com and ftp.cdrom.com, among others) from a command-line FTP client
> (running on Linux), the standard FTP control connection works fine, but the
> data connection (on 20/tcp) never gets established.
>
> The weird thing is that the control connection reports "No route to host" after
> it fails to connect back to my client on a high port. No traffic ever reaches
> the local LAN or the connecting router.

One bit of trivia that might help is that "No route to host" gets displayed
by *nix systems ONLY when they get an ICMP error message in response to a packet.
This could be "Port unreachable" or "Administratively prohibited" or 
"Time exceeded" - there's no telling from that message. You do _not_ get
that message by simply connecting to a host that RSTs it, which is 
what TCP stacks normally do when someone tries to connect to a closed port.

One wild guess would be that they block inbound connections, even though
they do say they don't, to ports below 1024. Have you tried opening the
data connection to a port >=1024 ?

The really weird part is that not even passive mode works. This would
suggest that they have a poorly written application level gateway in place,
that hates your typing char by char and rather expects commands to fit
in a single TCP segment (packet).

?

/Mike

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Mikael Olsson, EnterNet Sweden AB, Box 393, S-891 28 ÖRNSKÖLDSVIK
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