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Re: Net::FTP via CGI mystery

by rah (Monk)
on Jul 13, 2002 at 01:57 UTC ( #181434=note: print w/replies, xml ) Need Help??

in reply to Net::FTP via CGI mystery

Have you tried cranking up the debug level on Net::FTP? A 2 or 3 will give you a blow by blow account of the FTP session. Maybe that will give you some idea why it dies on the ls.

Also, and this may be insignificant, shouldn't
$ftp->ls be
$ftp->ls() ?
I don't know how this could make it behave differently on the command line vs. http, but that might be worth a try.

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Re: Re: Net::FTP via CGI mystery
by George_Sherston (Vicar) on Jul 13, 2002 at 12:52 UTC
    I tried increasing the debug level as you suggest, and it leaves me more baffled, but in a more specific way. First, I boiled down the script to the absolute minimum necessary to recreate the problem. It's now:
    #!/usr/bin/perl -w use strict; use Net::FTP; #use CGI::Carp qw(fatalsToBrowser warningsToBrowser); my $ftp = Net::FTP->new(""); $ftp->pasv; $ftp->login('xxx','xxx'); my @files = $ftp->ls('/tst') or die "could not do ls"; print "Content-Type: text/html\n\n"; print "$_\n" for @files; print "done\n";
    Now, it still works fine when run from the command line, and fails when run from the browser. When it fails in the browser I just get an internal server error, because I deleted CGI::Carp, but reviewing the error logs shows the following (n.b. I tried this with a different ftp server too, so I really think that the problem is here):

    Output from the script when run from the COMMAND LINE

    Net::FTP: Net::FTP(2.61) Net::FTP: Exporter(5.562) Net::FTP: Net::Cmd(2.20) Net::FTP: IO::Socket::INET(1.25) Net::FTP: IO::Socket(1.26) Net::FTP: IO::Handle(1.21) Net::FTP=GLOB(0x81177a8)<<< 220 ULTRA FTP SERVER Net::FTP=GLOB(0x81177a8)>>> PASV Net::FTP=GLOB(0x81177a8)<<< 530 Please login with USER and PASS. Net::FTP=GLOB(0x81177a8)>>> user xxx Net::FTP=GLOB(0x81177a8)<<< 331 Password required for xxx. Net::FTP=GLOB(0x81177a8)>>> PASS .... Net::FTP=GLOB(0x81177a8)<<< 230 CyBo welcomes replicant xxx. Net::FTP=GLOB(0x81177a8)>>> PASV Net::FTP=GLOB(0x81177a8)<<< 227 Entering Passive Mode (XXX,XX,XXX,XXX, +XXX,XXX). Net::FTP=GLOB(0x81177a8)>>> NLST /tst Net::FTP=GLOB(0x81177a8)<<< 150 Opening ASCII mode data connection for + file list Net::FTP=GLOB(0x81177a8)<<< 226 Transfer complete. Content-Type: text/html /tst/graphics /tst/style /tst/images done Net::FTP=GLOB(0x81177a8)>>> QUIT Net::FTP=GLOB(0x81177a8)<<< 221 Goodbye.

    Error Log report when run from the WEB BROWSER

    Net::FTP: Net::FTP(2.61) Net::FTP: Exporter(5.562) Net::FTP: Net::Cmd(2.20) Net::FTP: IO::Socket::INET(1.25) Net::FTP: IO::Socket(1.26) Net::FTP: IO::Handle(1.21) Net::FTP=GLOB(0x8286474)<<< 220 ULTRA FTP SERVER Net::FTP=GLOB(0x8286474)>>> PASV Net::FTP=GLOB(0x8286474)<<< 530 Please login with USER and PASS. Net::FTP=GLOB(0x8286474)>>> user xxx Net::FTP=GLOB(0x8286474)<<< 331 Password required for xxx. Net::FTP=GLOB(0x8286474)>>> PASS .... Net::FTP=GLOB(0x8286474)<<< 230 CyBo welcomes replicant xxx. Net::FTP=GLOB(0x8286474)>>> PORT XXX,XX,XXX,XXX,XXX,XXX Net::FTP=GLOB(0x8286474)<<< 200 PORT command successful. Net::FTP=GLOB(0x8286474)>>> NLST /tst Net::FTP=GLOB(0x8286474)<<< 425 Can't build data connection: Connectio +n refused could not do ls at line 9. Net::FTP=GLOB(0x8286474)>>> QUIT Net::FTP=GLOB(0x8286474)<<< 221 Goodbye.
    So... it seems that what's happening is that when run from the browser the script doesn't go into passive mode (whatever that means)... but I thought it already was in passive mode. I'm completely out of my depth here, and I would be most grateful for a steer on how to get this to work.

    George Sherston

      The following extract from the wsftp help might clarify things a little?

      Passive Transfers (definition) Normally, when you connect to an FTP site, the site establishes the da +ta connection to your PC (the client). However, if the site allows pa +ssive transfers, you can have your PC establish the data connection. We recommend that you use passive mode for most transfers. Note that p +assive mode may be required for users who are behind some types of ro +uter-based firewalls or behind a gateway requiring passive transfers.

      My only thought is that maybe one way is bypassing a proxy/firewall and the other isn't? HTH.

        I don't *think* that's the problem, because in both cases the attempt to access the remote ftp server is coming from the same place - namely my script. The only difference is in where I'm calling the script from, as far as I can see. Also, it logs in to the remote ftp server either way I call it. But it seems that, called from the browser, it doesn't send a PASV command to the ftp server. I'm not sure why, or why this is a bad thing. But what I really want to know is... how do I make it work??

        George Sherston

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