FileZilla Forums

Hi there,
Filezilla has been great for years as I use it for transferring work related files to and from client servers. I'm using Windows 10 x64 1909.

In this case, the file server is an FTP server that 'requires explicit FTP over TLS' and a login/pwd. Downloads are fine. The uploads HAD been fine. My upload speed is max 3 MByte/second. I usually get 0.5 - 2.5 depending on traffic. Networks have been worse in the last few months. It had been a few weeks since I'd needed to upload files to that server.

Recently the following happens :

• The upload speed is instantly at 80-150 MByte/second.
• The upload completion indicator, the bar for an individual file in the processing queue, fills up in seconds for a 300-400 MB file, which is the filesize I'm usually dealing with atm.
• The upload times out after 10-20 seconds.
• Filezilla retries and asks me to pick Overwrite/resume/etc.
• Right now I have 99 retries configured in preferences because of this, pick Resume and the "Always do this" checkbox option in that dialogue window.
• I tested outside, anonymous FTP connections and local SFTP (Rebex tiny) connections. Those work fine.
• A second ftp client I tested is Total Commander. The same results for FTP over TLS, and the same positive outcomes for FTP and SFTP.
• Most importantly, I am the only user on the clients FTP server this is affecting, so I'm suspecting a system/update screw up or me 'optimizing' something to oblivion since I did get rid of some Windows bloatware recently as well. If only I knew which systems Filezilla relied on for FTP over TLS.
• Downloads and navigation are fine.

Does anyone know what could be happening here and/or how to fix this ?

What systems does Filezilla rely on for FTP over TLS ? It is the only affected method of filetransfer.

What happens if you try a larger timeout value?

Are you using any malicious firewalls or AV products that intentionally break TLS by playing man-in-the-middle?

A timeout value of 120 seconds changed little as far as I could see. The same behaviour, perhaps even the same amount of transferred data.

Could it be the data is being cached somewhere in the system and that's why the transfer rates rocketed up ?

As far as malicious stuff, nothing was installed either previously or now, to my knowledge. Windows Defender is running and the standard Windows firewall. Nothing extra really.