What is the standard ftp service of ubuntu server 12.04?

If i can still access via ftp (sftp in particular)

Despite the name, SFTP is not FTP. It's an entirely separate SSH file transfer protocol, usually hosted by sshd (on the usual SSH port).

Not to be confused with FTPS, which is FTP (over SSL) and would be hosted by vsftpd.

Run the following command:

netstat --listening --program

Note: You may get more information running it as root.

I would recommend to use following:

for sftp:

netstat -nap | grep -e ":22"

for ftp

netstat -nap | grep -e ":21"

These two commands will give you the programs that are listenning on ports 22 (ssh) and 21 (ftp)

My best guess is that in your case it is going to be dropbear or openssh listening on port 22

If you are looking for an sftp service, then vsftpd will most likely have nothing to do with it