I downloaded the vsftpd file (The latest vsftpd release is v3.0.3) and manually installed it.
I then started the server using the command ./vsftpd_v1 vsftpd_v1.conf
and terminated it using Ctrl-z. When I tried to start it again using the same command it showed the following error:
500 OOPS: could not bind listening IPv4 socket
I searched the error and found that it means that server is already is running so could not bind another. So I am trying to stop the server but are not able to do. Like if I directly install it then I can use service ./vsftpd_v1 stop.
When you pressed Ctrl-Z, you did not stop but rather suspend the server. You can list the stopped programs using jobs and can switch back to one with fg. You can find more information on jobs in the Bash manpage (man bash, see "Job Control").
Use Ctrl-C instead to abort your program.