530 Please log in with user and pass first

[bcantor]

I am using an old FTP client on a legacy system to connect to a number of different FTP servers.
I don't normally have problems connecting and doing what needs to be done.

Recently, I started connecting to an FTP server using Filezilla Server.
I'm seeing some odd behaviour.
Most of the time, the FTP client connects properly.
Periodically, it connects, but won't logon, and starts displaying
"530 Please log in with user and pass first",
and continues until it is interrupted.
for example:

Connected to 63.139.xxx.xxx.
220-FileZilla Server version 0.9.27 beta
220-written by Tim Kosse (Tim.Kosse@gmx.de)
220 Please visit http://sourceforge.net/projects/filezilla/
331 Password required for e***y
530 Please log in with USER and PASS first.
530 Please log in with USER and PASS first.
530 Please log in with USER and PASS first.
530 Please log in with USER and PASS first.
530 Please log in with USER and PASS first.
...etc

Again, most of the time the login works, but sometimes it doesn't.
Changing the FTP client isn't a viable option.
Any ideas?

[boco]

My only guess is that the client fails to send USER and PASS or the actual credentials correctly. The problem could be caused by timeouts on the client side.

Legacy systems (Win98, Win95, Win3.x?) are often older CPUs with low MHz, it can cause a lot of problems.

My 'most legacy' system is an 80386 with 20MHz and 8MiB RAM. The OS is Win95C and the FTP client is WS_FTP LE. It connects properly most of the time, sometimes it fails. Only option is to try again, nothing you can fix. It's hard enough to find software that works on these systems nowadays...