Re: Unix clients refused, Windows clients allowed...

i had a similar problem but not the same :
windoz cmd : ok
windoz iexplore : ok
linux cmd : ok
linux mozilla :
    421 Service not available, remote server has closed connection (used 
to get this error messages rarely)
or
    The connection was refused when attempting to contact 
<ftp.mycorp.com> (get this error message the most of the time)
distribution of error message (one rare and the other often) can be 
explained by session still left open on my ftp server until max user is 
reached, at this point service not available is displayed (mozilla is 
perhaps not able to display the tomany msg)

whilst I can see my ftp server still have the session open,... and 
latter (after a timeout) close the connection
and notting my mozilla can correctly connect to other internet ftp 
server (at least some, because I found some site not reachable in the 
same way - but I thought at this time the server was down...)
I suspect a prb on the mozilla client ftp
what is strange is the error message appear immediatly, no timeout seems 
to be in effect...
I would make an ftp session with a tcpdump to see what occur exactly
but I need time...

also
when i connect on my local address to the server (not the public) it works 
linux mozilla : ok
so, I suspect a prb in the way mozilla interpret or negociate the 
passive address and port or something like that

note : I use Mozilla 1.0... (perhaps not the best thing)
    Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.0) Gecko/20020623 
Debian/1.0.0-0.woody.1

 > if you try to access your ftp server behind a firewall, try to log 
rejected/dropped packets or do a netstat -t on your ftp server and try 
to identify connections that try to be with the client
 > also try another ftp client, there is a lot of ftp client that you 
could try to figure out if it is a single machine prb, single software 
prb or general to the robustness of unix
 > also, if your error message come out after a long timeout, it could 
be because the passive negociation failed, or also because the wu-ftp 
tries to reverse resolv the name of the ip addr of the client (you can 
disable this feature with "timeout RFC931 0"
I THINK THE REAL PRB COULD BE :
 > i know some new capabilities had been added recently to ftp server 
"extensions" (new command that wu-ftp implement)
for example EPSV command :
when i logged correctly on my ftp server and do the 1st ls
<<
ftp> ls
500 'EPSV': command not understood.
 >>
for extensions, see :
<<
EPSV and other new extensions are described in rfc 2428 available from rfc
repositories everywhere (eg
http://www.cis.ohio-state.edu/htbin/rfc/rfc2428.html)
 >> found in wu-ftpd forum 
(http://www.landfield.com/wu-ftpd/mail-archive/wuftpd-questions/2000/Dec/0141.html) 
:)

what could arrive is our client (my mozilla and your cmd) are anyhow 
paniced when they receive this command and
instead of stating the command is not understood, interpret it as a 
connection closing...

 >> IF ANY ONE KNOW HOW TO DISABLE THESE EXTENSIONS, THANX TO TELL US

btw Sun Download Manager expect the same prb : I can see connection 
attempt in my logs but logon fails

hth


Ted Keller wrote:

>Tom
>
>
>This message comes from your ftp client....
>
>
>strings /usr/bin/ftp | grep Service
>421 Service not available, remote server has closed connection
>
>
>This would imply that your client can't get to your ftpserver - or the ftp
>server can't respond back to your unix clients.
>
>You may want to verify your ip stack settings - and verify routing is
>consistent with your network topology.
>
>ted keller
>
>
>On Wed, 21 Apr 2004, Tom Wachs wrote:
>
>  
>
>>Hi all,
>>
>>
>>
>>  I have a server running Solaris 8 and wu-ftpd 2.6.2 (through tcp
>>wrappers) that I'm having some trouble with.  I can connect with a
>>Windows client, from a Windows command prompt, or from a telnet session
>>from a Windows box.  I cannot connect from a *nix ftp client or through
>>telnet from a *nix command prompt.  The error message I get from the
>>*nix ftp client is:
>>
>>
>>
>>421: Service not available, remote server has closed connection
>>
>>
>>
>>TCPWrappers does not log a connection attempt for the *nix clients,
>>although it does log connections from the Windows clients.
>>
>>
>>
>>I am running the wu-ftpd server from inetd with the following line:
>>
>>
>>
>>ftp     stream  tcp     nowait  root    /usr/local/bin/tcpd    in.ftpd
>>-a
>>
>>
>>
>>A port scan from another *nix machine shows port 21 open for ftp.
>>
>>
>>
>>Has anyone seen this type of behaviour before? Can anyone suggest
>>something?  I'm running out of ideas.
>>
>>
>>
>>Thanks in advance,
>>
>>
>>
>>-Tom
>>
>>------------------------------------------
>>
>>C. Thomas Wachs
>>
>>PAR3 Communications
>>
>>Phone: 206-902-3944
>>
>>E-Mail: [email protected]
>>
>>
>>
>> -o)
>>  /\
>>
>> _\_v
>>
>>
>>
>>
>>    
>>
>
>
>  
>