Re: FTP from AS400 to Unix with data connection error

[Scott Klement <klemscot@xxxxxxxxxxxx>]

I've experienced this error before, but it was always a firewall issue.

In the FTP protocol, the FTP client and server connect on port
21, and this is called the "control connection".  On that port
they negotiate which FTP commands (such as put, get, rename,
delete) will be executed, as well as which files will be sent to
which directories, etc.   When a file transfer takes place, they
negotiate an address & port to use for a "data connection", which is
used to transfer that one file, and then closed.    For each transfer,
they negotiate a new port/address for the data connection which may be
the same ports, but also may be different.

If there is a firewall in between, they may be negotiating a port that
the firewall does not permit.   When this happens, the negotiation
succeeds, but when they try to actually open the data connection, they
can't connect -- thus the message "can't open data connection"

I don't know if this is the same problem that you're encountering, but
that's what it was for me.   The fix might be to simply re-try when it
fails, or to change the firewall.

HTH

On Wed, 27 Mar 2002, Lori Hainey wrote:

> We have a process that FTP's various files from our AS/400 to a vendor's
> Unix box. Some of the files transfer fine, others bomb out with a '425 Can't
> open data connection' error. We are doing to STRTCPFTP within a CL and
> taking the default parms on this command (of which one is WRTRMNOPN) meaning
> the value in the record parm is written tot the file and the member remains
> open. I am thinking this may be our issue and if I change to *WRTCLOSE
> (value in record parm is written to file and member is closed), that this
> may resolve the issue. I just wanted to see if others have experienced this
> issue before and what their experience has been to consider all options for
> resolution.
>
> Lori Hainey
> Project Leader
> York International
> lori.hainey@york.com
>