Network Config-Wizard fails because of a 503

[eagle3386]

Hi,

tried to use the wizard and it always fails because of
this:

Connecting to probe.filezilla-project.org
Response: 220 FZ router and firewall tester ready
USER FileZilla
Response: 331 Give any password.
PASS 3.0.0-beta2
Response: 230 logged on.
Checking for correct external IP address
Retrieving external IP address from
​http://ip.filezilla-project.org/ip.php
Checking for correct external IP address
IP 84.180.193.90 ie-bia-bjd-ja
Response: 200 OK
PREP 33860
Response: 200 Using port 33860, data token 168251198
PORT 84,180,193,90,132,68
Response: 200 PORT command successful
LIST
Response: 150 opening data connection
Response: 503 Connection failed.
Server sent invalid reply.
Connection closed

So, AFAIK an 503-error means that the service is
unavailable.. So a fix would be nice.

Thanks in advance,

Martin.

[Tim Kosse]

It means you got a rampant router or firewall preventing you
to accept incoming connections. Fix your router/firewall
configuration and the wizard will succeed.

[Tim Kosse]

Supplemental: Error message from server has to be claried to
avoid confusing users.

[eagle3386]

But AVM (manufacturer of my router) clearly says that I
don't need to create a port forwarding-rule for FileZilla.

Additionally, doing so (creating a rule) results in a
problem already submitted as a bug report to the FZ3-bug
database and to AVM, too.
And the bottom line from the mails I wrote to (and received
from) AVM was that there can't be a problem with the
Fritz!Box itself since the router only takes packets
incoming on port X and moving them to port Y..

So, to give AVM's support more information, I'd like to know
as much stuff as possible about this wizard, how it works
(Maybe a source code-snippet?) and all this stuff - that
would be very kind of you because it would allow me to give
AVM's support-guys the link to this tracker-item so that
those guys can follow-up this issue and (if needed) release
a fix to get this bug (either in FZ or the router) fixed
quickly..

[Tim Kosse]

But AVM (manufacturer of my router) clearly says that I
don't need to create a port forwarding-rule for FileZilla.

And the bottom line from the mails I wrote to (and received
from) AVM was that there can't be a problem with the
Fritz!Box itself since the router only takes packets
incoming on port X and moving them to port Y..

Both paragraphs conflict each other. First paragraph implies
protocol guessing (which is dangerous), wheras the second
paragraphs inplies port forwarding neccessary.

Automated protocol guessing is dangerous because the
router/firewall has no guarantee that the guess is correct.
So unless the user explicitly tells the router/firewall that
the used protocol is FTP, the router/firewall has absolutely
no rights to modify any data (Yet lots of routers and
firewalls do).

To combat this, the network configuration wizard has been
specifically crafted to detect configuration problems. It is
on purpose different than normal FTP. While automated
protocol guessing (which can never be fully correct) may
work in most cases, it fails as soon as the protocol changes
or if for example encrypted FTP is used, where the
router/firewall can no longer tamper with it.

While most users will be able to use FTP even if the wizard
fails, compatiblity with each and every server can only be
guaranteed if the wizard succeeds.
Any attempts by router or firewall manufacturers to work
around the testing protocol will only result in hidden
incompatibilities.

That said, the wizard's souce can be found at the following
URLs, the code is licensed under the GPL.
Client side:
​http://filezilla.cvs.sourceforge.net/*checkout*/filezilla/FileZilla3/src/interface/netconfwizard.cpp
Server side:
​http://filezilla.cvs.sourceforge.net/filezilla/probe/