cLive ;-) has asked for the wisdom of the Perl Monks concerning the following question:

Sorry to ask this here, but since it affects my transfer of scripts between my machine and clients, it's a sort of Perlish question and I thought others may have experience of it :)

Some sites I connect to force me to use passive mode when using FTP, some don't. I sometimes forget to change mode locally, or can't remember whether the server requires passive or not (probably more likely :)

Sometimes, it seems I can transfer files, even if I'm in the "wrong" mode, but when they get transferred, they get corrupted, with (seamingly) random parts of the script getting repeated throughout.

I'm using GFTP to up/download. To keep this short, is this:

Has anyone else experienced something similar? Or should I just get a different FTP client? If so, recommendations?

thanks

cLive ;-)

Oooo, back on topic now: 

print "Just another Perl hacker"

[download]

Replies are listed 'Best First'.
Re: OT question - FTP problem
by Anonymous Monk on Jun 07, 2001 at 00:23 UTC
    It's a firewall issue.
[reply]
      Any chance you can elaborate on this answer?

      "Give a man a fish, and all that..."

      cLive ;-)

[reply]

        Your anonymous friend is partly right: the passive ftp requirement is a firewall issue. ftp connections join two arbitrary high ports on the client to ports 21 and 20 on the server. For some weird reason, in normal ftp the second of these - the data connection - is initiated by the server, and doesn't even have to return to the same machine as the control connection. Indigestion for the firewall administrator on the client side: you have to leave 1024-65535 open and try to distinguish legitimate ftp connections from sinister exploration.

        in passive ftp both connections are requested by the client in the proper way. more headache on the server, because the data connection goes to a high port there, but the range of options can usually be circumscribed. the client-side firewall is much simpler and more secure because it can open the relevant port from the inside, rather than having to remain alert to ouside requests across a broad range of ports that it would rather just block and forget about.

        so i'm puzzled for two reasons: why do you only have to use passive sometimes? i'd have thought that would depend on _your_ firewall and be the same for all outward ftp connections. i've come across servers that will only do active, but never the other way round. And i _really_ can't imagine why you would sometimes be allowed to connect the wrong way.

        so i can clarify, but not help one tiny bit. sorry.

        ps. back on topic: i think that's the first japh on the site i was able to read. But remember, adding 'use strict;' at the top of your script will alert you to common errors and sloppiness before you get into trouble.

[reply]

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