Why can I obtain file size and the time stamp with FTP but not be able to retrieve the actual file? - php

Question

I've been working on this for about 20 hours now and I need some major help. I'm able to get the file size and the timestamp on the file but I am unable to actually obtain the data.
The server I'm trying to get the data from requires FTP over explicit TLS
I'm receiving the same error(s) with both FTP_BINARY and FTP_ASCII in the ftp_fget()
The server the file is coming from is UNIX
If I refresh the page every few hours the errors I get from PHP are different with no change in code
Error 1: 'ftp_fget(): Transfer mode set to BINARY if ftp_get is binary
or it's 'ftp_fget(): Transfer mode set to ASCII' if ftp_get is ascii
Error 2: 'ftp_fget(): Entering Passive Mode(12.345.678.90.12.34)'
On the above errors I read that PASV mode being FALSE is what triggers Error 1, so I think the switching between the errors is for pasv mode working or not working. Not positive though.
<?php
$server = "12.345.678.90";
$local_file = 'inv3.txt';
$file = 'inventory-alp.txt';
$con = ftp_ssl_connect($server,21) or die("Could not connect to $server");
ftp_login($con,"xxxxxx","xxxxxx") or die("Could not login");
ftp_pasv($con,true);
$fsize = ftp_size($con, $file); // works
if ($fsize != -1)
{
echo "</br>$file is $fsize bytes.</br></br>";
}
else
{
echo "</br>Error getting file size.</br></br>";
}
$lastchanged = ftp_mdtm($con, $file); //works
if ($lastchanged != -1)
{
echo date("F d Y H:i:s.",$lastchanged)."</br></br>";
}
else
{
echo "Could not get last modified</br></br>";
}
if (ftp_get($con,$local_file,$file,FTP_ASCII)) //fails
{
echo "successfully written to $local_file";
}
else
{
echo "There was a problem while downloading $file to $local_file";
}
$var = error_get_last();
echo '<pre>';
var_dump($var);
echo '</pre>';
ftp_close($con);
?>
EDIT 1: Solution: I ended up not being able to access what I needed to change the firewall settings and such in php. While this is not the true answer, I did make it work and it is relatively easy.I ended up running across WINSCP, having the ability to connect to the server in a filezilla type layout and then save the session url was nice. All i did was access the saved session in the .exe and was able to set up my connection in half an hour.

Answer 1

What Martin indicated is very true, the SIZE and MDTM commands run synchronized over the main FTP Command Connection only. The transferring of data files, and usually the directory listing also (unless MLST/MSLD is used) requires a separate connection, the Data Connection, which is negotiated by the client and server over the Control Connection using a series of commands, most notably PORT and PASV.
Without going into a ton of detail (There's a link to our white paper later), when the Client & Server negotiate the terms of the Data Connection, one of the end points will tell the other endpoint the specific IP address and Port number for the connection. One endpoint will listen and wait for a connection from the other endpoint. This works great unless there is a firewall in front of the endpoint that is waiting for the inbound connection. If the client/server session is running in Active mode, the Server will actively connect back to the client on the IP/Port which was received by the server from the client in the form of the PORT command. In Passive mode, the Server will passively wait for the client to connect on the IP/Port which was sent by the server to the client in the response to the PASV command sent by the client to the server.
Again, firewalls tend to block FTP data connections, unless the firewall does active FTP NAT'ing or unless Port Forwarding has been set up on the Firewall and a set of passive-ports has been opened and routed to the endpoint specifically.
So check the firewall settings on the client if you want to use Active/Port mode; check the firewall settings on the server if you want to use Passive/PASV mode.
Here's a link to our white paper which outlines the basics of FTP/PASV/PORT, hopefully it'll help you with your issue.
http://www.webdrive.com/wp-content/uploads/FTP_Explained1.pdf
Best of Luck!
Michael

Answer 2

With the FTP protocol, it's perfectly possible that you are able to obtain the file size and the modification timestamp (using SIZE and MDTM commands respectively), but not the file itself.
The SIZE and MDTM commands use the FTP control connection only.
While a file transfer (or a directory listing) requires a separate data connection. And it's likely that there's something that prevents the data connection from being opened.
See (my) article on the FTP connection modes for more details and typical issues with data connections.
Typically a culprit would be a firewall on your webserver. If you have an SSH/terminal access to the webserver, are you able to connect from it to the FTP server?
Another possibility is a misconfigured FTP server. Is the IP address in "Error 2" routable from your web server? (=Is it the real IP address you connect to?)
It is unlikely this is related to an ASCII/BINARY mode. The messages you are getting (Transfer mode set to ...) are status messages, not error messages. They are not related to your problem. It's indeed strange that you got no other message/error.
You can try to use the active mode, instead of the passive.
ftp_pasv($con, false);
But usually the active mode is more problematic.