Invisible Login

[greep%su-dsn at sri-unix.UUCP]

If you don't need the features of getty (eg detecting upper-case only
terminals) or login (accounting and creating an entry in utmp), and if what
you want is one tty line (I assume that's what you mean by "port") to
always run the same program, then instead of trying to fake a login, you
could disable that line for logins and put an entry in /etc/rc that starts
up your program talking to that line.  If the program is one that could
possibly terminate, then you could instead start up a shell file which just
runs that program in a loop, so that if it exits, a new copy starts up
again. (You would probably also want it to change the uid.)