"421 Service not available, remote server has closed connection" when trying to transfer data

When I try to login via vsftpd_v2 server it successfully logs me but when I try to use ‘get’ or ‘put’ it throws the above error and closes the connection. Please help, I am stuck here for more than a day.

Also it works for servers vsftpd_v1, vsftpd_v4, vsftpd_v5 and vsftpd_v6. Only 2 and 3 number servers are problematic.

421 Service not available error, when using GET in vsftp_v2 this might help you.

this probably means that there is a port running already on the machine that causes this fail. try to close the vsftpd process and try again

some versions are faulty. remember that

refer this : 421 Service not available error, when using GET in vsftp_v2

Ok so some versions are faulty. So am I supposed to mention them in the files high_cpu_usage_versions , increased_time_taken_versions etc. because they just refuse to transfer files?

No mention the faults in specific files.
Like when asked for memory mention only those version with faulty or abnormal memory usage.
When asked for cpu then mention only those with abnormal cpu usage