wodFtpDLX.Net: slow connection and timeouts (wodFtpDLX / wodFtpDLX.NET)

Hi all,

We use wodFtpDLX for a number of connections without problems, but recently noticed an issue with certain servers.

The remote SFTP server in question is using Tectia SFTP - their server reports this version at logon: "Server version: SSH-2.0-6.4.14.26 SSH Tectia Server"

Our connections work fine using wodFtpDLX 1.8.4.248 on Windows 2012 R2. Connect/push file/rename file/disconnect in about 1 second.

However running the same software on Windows 2019 we get long delays during connection and when pushing and renaming files. This can easily take 60 seconds per step, but sometimes even longer and we get a timeout.

We have seen the same behaviour with wodFtpDLX 1.9.0 on Win2019.

Has anybody else seen this type of issue?

Thanks.

Hi.

When do you see delays, do they happen sometimes with that server, or each time? If you try this server against our sample code apps, does same thing happen?

Jasmine

Hi Jasmine, thanks for the response.

We see slow connections and/or timeouts consistently when connecting from Win2019 to that specific server.

We don't see it when connecting to other servers from Win2019, and we also don't see it when connecting to that server from Win2012 R2.

We've been using a test harness based on our own code, but I'll try it with your sample code - thanks!

Just to verify, seeing the same results with the VB.Net sample code (modified only to set licence key and to specify Protocol as SFTP).

Thanks.

We've been using a test harness based on our own code, but I'll try it with your sample code - thanks!

Hi.

Ok, in order to isolate this issue I'd like you to check if connection is idle for that amount of time, or simply transfers are slow. I assume you perform a file transfer when this happens. If you check Progress event, does it fire and does it actually transfer files, or everything just stops?

Any chance we could connect to that server for a test?

Regards,
Jasmine.

Hi Jasmine,

If we use events (blocking mode off) then we don't see the Connected, Done or Progress events fire.

Our network guys said the remote server is sending many retransmissions of the same packets during the connection and later stages (on the rare occasions it connects).

Unfortunately it's not our server, so we can't give you access to it, though I will ask them. Not sure if it's possible to get a trial of the Tectia SFTP server software to try it. https://info.ssh.com/tectia-ssh-server-trial-download

Thanks

Hi.

If you see many re-transmissions, then this sounds like socket issue, not application issue. Do you have any other connections (not SSH or SFTP) to that server, how does that work?

From application's perspective, we can't even interefere with raw (TCP) packets, we can simply Connect, Send, Receive, Disconnect.

Jasmine.

Thanks.

We have tried connecting using other SFTP clients such as psftp

That is successful, so it appears to me to be a combination of SFTP client running wodFtpDLX on Win2019 Server + Tectia SFTP server

We'll keep digging, but any other suggestions very welcome!