Ftp failed to retrieve directory listing

[Senator Sibbuku]

Am trying to connect to the DSS200 showstore to upload keys. An its saying FAILED TO RETRIEVE DIRECTORY LISTING. Is there a way to resolve this?
or
Is there a way I can ingest keys remotely.

[Leo Enticknap]

The gotcha is that you have to connect in active mode, not passive. Assuming that you're using Filezilla, these settings work for me:

DSS200_FTP_1_nopassword.jpg

DSS200_FTP_2.jpg
If the media block is a cat745, you can't ingest a KDM while it is playing. I don't know what happens if you try via FTP: whether it just discards it and you have to try again after playback stops, or it automatically processes it after playback stops.

[Senator Sibbuku]

Thank you Leo, but did not work for me. I tried it, still not connecting.

[Brad Miller]

Make sure you are using regular FTP, not SFTP. The port number has to be 21.

[Senator Sibbuku]

Ok, once tested tomorrow will let you know. Thank you

[Senator Sibbuku]

I tried to follow the advice, but still not succeeding, I even used Wing FTP rush but still no success. Any reasons why this is happening?

[Leo Enticknap]

The DSS200 does not use port 59981 for anything, that I'm aware of.

[Marcel Birgelen]

The DSS200 does not use port 59981 for anything, that I'm aware of.

It does, for active FTP

Active FTP opens up a "random" port from the FTP server back to the FTP client, that's why Active FTP is such a horror to run through firewalls. Some firewalls and gateways do have FTP helpers, but those break once SSL/TLS comes in to play. (Or some of them are just crappy implementations that tend to randomly crash or find other ways to annoy you: In general, you should avoid "helpers" like FTP or SIP helpers like Covid19.)

@Senator Sibbuku: Are you on the same subnet as the DSS200? If not, it's probably the device or one of the devices between your networks that is not allowing you to do active FTP. You may try to use Passive Mode as a way around this, the DSS200 should support both. But Passive FTP also comes with firewall requirements...

Also, make sure it's not a local firewall or security software on the client blocking the incoming active FTP requests.

[Leo Enticknap]

Thanks. In order to connect to a DSS200 in the past using Filezilla set to an active connection, I have only had to ensure that ports 20 (plain FTP data) and 21 (plain FTP commands) are unimpeded in the switches and firewalls between the computer and the DSS, and everything has worked OK. I found this about ports and active FTP:

active_mode_FTP.jpg

In Senator's case, the error message is "No connection could be made because the target machine actively refused it." Maybe what is happening is that his PC is addressing port 59981 (and then later, 58971) on the DSS200, rather than using that as the originating port? In any case, it seems that the two computers are communicating with each other. If they weren't, surely the attempt to connect would simply time out rather than return that message? Agreed that a misconfigured managed switch, router, or firewall getting in the way is the most likely source of the trouble. This could be ruled out by connecting a patch cord directly from the PC to the either the auditorium or theater LAN port of the DSS200 (FTP will work on either - it doesn't have to be the designated management LAN), ensuring that both are configured to be on the same subnet, and trying again.

You may try to use Passive Mode as a way around this, the DSS200 should support both.

I was told by Dolby Technical Support that it didn't, and that you had to use active. This was a long time ago (2014 or '15, most likely), and I guess that support for passive may have been added to a later DSS software version. The problem I was getting that caused me to contact them was that by connecting from Filezilla in passive mode, it would retrieve and display directory listing, but would not transfer any actual files, either up or down. After switching to active mode everything worked, and I've used that ever since when connecting from a PC to a DSS server using FTP.

[Marco Giustini]

What Marcel says.
If this is remotely via VPN or something like that it’ll take an awful lot of effort to configure active ftp on the firewall.

do start from a direct connection to the server: does that work?

[Marcel Birgelen]

In Senator's case, the error message is "No connection could be made because the target machine actively refused it." Maybe what is happening is that his PC is addressing port 59981 (and then later, 58971) on the DSS200, rather than using that as the originating port? In any case, it seems that the two computers are communicating with each other. If they weren't, surely the attempt to connect would simply time out rather than return that message? Agreed that a misconfigured managed switch, router, or firewall getting in the way is the most likely source of the trouble. This could be ruled out by connecting a patch cord directly from the PC to the either the auditorium or theater LAN port of the DSS200 (FTP will work on either - it doesn't have to be the designated management LAN), ensuring that both are configured to be on the same subnet, and trying again.

The message comes from the server on the DSS200. For the active FTP data connection it will open a new TCP session originating from port 20 (the FTP data port) to a random port on the client. It will communicate this port via the existing control connection (FTP port 21).

You see that the FTP server tries to connect to the client twice, once on destination port 59981 and once on 58971.

The message that the "target machine", as in, the client actively refused the connection is an indication something is sending an ICMP message indicating that the port is unreachable. Usually, a packet-filter type firewall, would silently drop the traffic without sending a reply, which would've resulted in a timeout rather than this message.

Still, in order to debug the situation, like Marco also correctly indicated, he should make sure he's connecting from the same network. If the error is still the same, the problem is on the client machine.

I was told by Dolby Technical Support that it didn't, and that you had to use active. This was a long time ago (2014 or '15, most likely), and I guess that support for passive may have been added to a later DSS software version. The problem I was getting that caused me to contact them was that by connecting from Filezilla in passive mode, it would retrieve and display directory listing, but would not transfer any actual files, either up or down. After switching to active mode everything worked, and I've used that ever since when connecting from a PC to a DSS server using FTP.

I may also be confusing things, but Passive FTP has been around since 1997, when it was introduced as a way to get around the problems with NAT and Active FTP. It would be strange for Dolby to implement their own FTP server and not just take one of the many good implementations out there, which include support for Passive FTP, out of the box.

[Senator Sibbuku]

My Apologies, wasn't feeling well. Missed the conversations on time. Never the less, the problem has been the firewall on my file server. I had done everything advised, set it to active etc. If I disable firewall everything works without any issue. Am yet to set it accordingly for the FTP ports. Otherwise your responses has been of tremendous help.