FileZilla Forums

When I upload a larger file the progress bar immediately fills to 100% and no activity, time or data rates are displayed. Although the file transfer works anyway, after 20 seconds the set time out takes effect and FileZilla reconnects and asks what to do with the file. If "Resume" is always selected here, the upload can be fully completed at some point.

What could be the reason that FileZilla no longer recognizes that the file transfer is running? Since I had not uploaded a larger file for a long time, I can unfortunately not say up to which version the detection worked.

[FileZilla 3.55.0 (64-bit), Windows 10 21H1 (64-bit)]

Is it possible that the issue is with the server? After the recognition stopped working even with older versions, I connected to another server and it worked right away. The difference: this server uses SFTP, the other FTPS. If I switch the other server from FTPS (explicit) to SFTP, the recognition works again!

Is the issue now only with the server or can FileZilla possibly be modified so that the detection of the transfer also works with FTPS (explicit)?

Issues like this are typically caused by faulty firewalls or NAT routers dropping the connection prematurely without informing both ends.

If you are using any firewalls or NAT routers, be it client- or server-side, please uninstall/remove them for a test.

Thank you for the answer.

However, neither NAT nor Firewall can be disabled on my router. And I do not have access to the server side (since it is a web hoster).

However, the file transfer is not aborted by NAT or Firewall, but follows exactly the time out set in FileZilla. The log therefore also always states that inactivity was detected and a new connection is therefore made. And that although the file transfer runs in the background without errors! The problem seems to be that FileZilla itself does not recognize this file transfer as active.

The end of the transfer is signaled by closing the data connection. If some firewall or NAT router drops the connection instead of orderly forwarding the close notification to both peers, the client will eventually run into a timeout.

The connection is certainly not dropped by NAT or Firewall. Because if I change the time out in FileZilla to 10 seconds, FileZilla reconnects after 10 seconds. If I change the time out to 30 seconds, then after 30 seconds and with 60 seconds only after 60 seconds... If the time out is large enough, the complete file can be uploaded without errors and without a reconnection.

FileZilla interrupts the file transfer by itself exactly after the set time out, because FileZilla for whatever reason does not recognize that a file transfer is running. Although the file transfer is running in the background but without errors.

Hello, did you manage to solve this problem?

I have exact same issue:
Everything that exceeds ~300-400mb size uploads in a seconds and then just stuck, or getting transfer failed message, but uploading is still proceed in background, i can watch it through task manager (resource monitor) or just refresh remote directory and file size are grow. This is so strange behavior, i think it maybe relative to SSD caching or something like that.

And by the way, i manage successful upload of exact same files on both Manjaro Linux and macOS Mojave systems, same home network, same remote server.

So in my case only Windows machines acting like that...

### UPDATE

Changing transfer mode to Active seems like solved the issue for me, now uploads goes normally and FileZilla UI shows progress correctly till the end, tested on 2 different servers.

Are you using any firewalls or AV products?