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Why do my FTP transfers all freeze up?

I've been trying to copy some files off an FTP archive, but every time I go to do the transfer, it says "Entering Extended Passive Mode" and never gets any further. My conclusion: this passive mode thing is a bust. How can I transfer the files without using passive mode? I'm using ftp from within a Terminal on my Mac, by the way.

Dave's Answer:

This is a somewhat common problem with FTP, actually, and while I admit that I'm not entirely sure what passive mode is either, I do know how to get around it within the ftp program. Here's an example of me grabbing a file from the O'Reilly Media server:

$ ftp ftp.oreilly.com
Connected to ftp.oreilly.com.
220 ProFTPD 1.2.10 Server (ftp.oreilly.com) [172.31.173.9]
Name (ftp.oreilly.com:taylor): ftp
331 Anonymous login ok, send your complete email address as your password.
Password:
230-Welcome to the O'Reilly & Associates, Inc. FTP Archive.
230 Anonymous access granted, restrictions apply.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> get /demo/demofile.zip demofile.zip
local: demofile.zip remote: /demo/demofile.zip
229 Entering Extended Passive Mode (|||64758|)

That's as far as it gets. Like you, my connection hangs. Fortunately, fixing it is as easy as typing in a single command into the ftp program: EPSV.

Now watch what happens:

^C
receive aborted. Waiting for remote to finish abort.
ftp> epsv
EPSV/EPRT on IPv4 off.
ftp> get /demo/demofile.zip demofile.zip
local: demofile.zip remote: /demo/demofile.zip
227 Entering Passive Mode (209,58,173,9,252,250).
150 Opening BINARY mode data connection for /demo/demofile.zip (4908794 bytes)
100% |***************************************************| 4793 KB 163.08 KB/s 00:29
226 Transfer complete.
4908794 bytes received in 00:29 (162.48 KB/s)
ftp>

That's all there is to it. Hope that helps you get your FTP transfers going again too!

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Comments

That may fix it, and may not.

FTP gets ugly on today's Internet, because it was designed in the 1970's, long before firewalls were common and before Network Address Translation (NAT) existed. The near universal use of firewalls and NAT on the Internet today make FTP problematic at times.

This document explains the issues and work arounds very well.
http://www.ncftp.com/ncftpd/doc/misc/ftp_and_firewalls.html

Posted by: Chris Buechler at April 8, 2006 8:52 PM

FTP Passive mode is used by most FTP programs with the prevalence of firewalls. The FTP protocol uses 2 ports (one for transfer one for control). When a file is requested the requestor sends a message to the server on the control connection. Then the server responds to the receiver by initiating a transfer connection to the requestor... but if there is a firewall, the transfer connection can't be made since the firewall will likely block it. So passive mode adds some protocol steps where the server opens up a port for the requestor to connect to for the transfer connection, sends that information to the requestor over the control channel, and the requestor makes the transfer connection. So in passive mode, all connections to the server are initiated from the requestor so they are allowed by the firewall.

Posted by: TD at April 18, 2006 8:38 AM

On my Mac OSX 10.4.8, this failed:

ftp> EPSV
?Invalid command.

HELP!!

Also, is there a way to configure this automatically?

Posted by: Tom Schneider at December 15, 2006 1:03 PM

Oh, it accepts lower case!

ftp> epsv
EPSV/EPRT on IPv4 off.

but it still hangs in 'Entering Passive Mode'.

Eventually it said

200 PORT command successful.

421 Service not available, remote server timed out. Connection closed
ftp>

Interestingly it created an empty file on the
remote computer where I was putting the file.

Posted by: Tom Schneider at December 15, 2006 1:08 PM

I'm experiencing this problem with two FTP servers. The EPSV off fix works fine one one (dataflame.co.uk) but failed on the other (p4host.com).

I have tried turning the OSX firewall off completely but this makes no difference. I have tried the terminal, Cyberduck and Yummy FTP -- same problem with all of them.

I'm running OSX 10.4.9 on an Intel Mac.

Can anyone help?!

Posted by: Lylo at March 24, 2007 3:09 AM

The general rule is that if you have a local NAT/firewall you'll want to use passive mode, and if you have a remote firewall, you'll probably need to use active mode.

EPSV is a function of the remote server. If EPSV isn't working for your specific remote server, try PASV.

Use the PASV and EPSV command to cycle passive mode off and on. Passive mode is on by default in most FTP clients.

Posted by: James Howard at November 30, 2007 1:27 PM

Thanks Dave,
This worked perfectly on the Solaris box we were grabbing data from! Had tried quote PASV before with no success.

Posted by: Lane at December 6, 2007 8:57 AM

I have a lot to say, but ...

I have a lot to say, and questions of my own for that matter, but most of all I'd like to say thank you for all your efforts on this Web site by buying you a chai!

I do have a comment, now that you mention it!