ttys file question

[Jack Mc Lauren]

Hi list

I'm trying to connect to my server via a serial port which is named ttyu6 under FreeBSD. In order to do that, I've decided to change /etc/ttys file like this:

# Serial terminals
# The 'dialup' keyword identifies dialin lines to login, fingerd etc.
ttyu6   "/usr/libexec/getty std.115200" cons25  on secure


But I can not connect to my server with this configuration. But if I change ttyu6 to cuau6, everything works fine! I don't understand the difference, would you please explain the reason for me?

Thanks in advance