[ILUG] half working tftftfftp

[Gavin McCullagh]

On Mon, 08 Oct 2001, Ulysees wrote:

> have a very strange problem with my tftpd
> on the local machine i can tftp to myself and download a file ok
> when i try to upload a file it doesn't work, it will create a 0 length file
> in the tftproot but nothin more
> 
> Anybody ever come across this ? seems a bit odd
> 
> uly

This is something I was told by a friend at some stage.  

Try doing it in passive mode.  You may find you're going through a firewall
somewhere.  I'm not totally sure of the technical bits, but I've a feeling
it causes the client to be flexible about the port and allow the firewall
to set it or something like that.

As I say, I don't honestly understand in detail, but this sounds like the
problem I had.  From the ncftp man page:

       passive
              This controls ncftp's  behavior  for  data  connec­
              tions,  and  can  be  set to one of on, off, or the
              default, optional.  When passive mode is on,  ncftp
              uses  the  FTP  command  primitive PASV to have the
              client establish data connections  to  the  server.
              The default FTP protocol behavior is to use the FTP
              command primitive PORT which has the server  estab­
              lish  data  connections to the client.  The default
              setting for this variable, optional,  allows  ncftp
              to choose whichever method it deems necessary.




   FIREWALL AND PROXY CONFIGURATION
       You may find that your network administrator has placed  a
       firewall  between  your machine and the Internet, and that
       you cannot reach external hosts.

       The answer may be  as  simple  as  setting  ncftp  to  use
       passive  mode  only, which you can do from a ncftp command
       prompt like this:

            set passive yes

       The reason for this is because many firewalls do not allow
       incoming  connections  to  the site, but do allow users to
       establish outgoing connections.  A passive data connection
       is  established  by  the client to the server, whereas the
       default is for the server to establish the  connection  to
       the client, which firewalls may object to.  Of course, you
       now may have  problems  with  sites  whose  primitive  FTP
       servers do not support passive mode.

       Otherwise,  if you know you need to have ncftp communicate
       directly with a firewall or proxy, you can try editing the
       separate  $HOME/.ncftp/firewall  configuration file.  This
       file is created automatically the first time you  run  the
       program,  and contains all the information you need to get
       the program to work in this setup.

       The basics of this  process  are  configuring  a  firewall
       (proxy)  host  to  go through, a user account and password
       for authentication on the  firewall,  and  which  type  of
       firewall  method  to use.  You can also setup an exclusion
       list, so that ncftp does not use the firewall for hosts on
       the local network.

Gavin