Modems and carriers in BSD

[Kristoffer Eriksson]

How does BSD handle the carrier on tty ports?

I'm working on the next version of C-kermit, rewriting the parts that
are concerned with tty communications. I'm used to System V and Xenix,
but have no experience with the BSD environment. Unfortunately, somewhat
surprisingly, no one else in the work group seems to really know how it
works, either. We thought the earlier versions were working in the
BSD environment (although they didn't work quite right in the System
V environment, which is what pulled me into this), but now we discovered
that we really don't know whether it does, or if it does, how.

So, how do you program for using a modem on a BSD system? Sometimes you
want talk to the modem regardless of the carrier (that is while dialing),
and sometimes you want to be notified when the carrier drops (that is
while talking to a remote host). On System V the CLOCAL bit in the
termio tty parameters controls this behaviour. BSD systems don't have
termio. How do you do it in BSD?

The man pages have not been sufficient to enlighten me. They don't
describe how BSD reacts to the carrier state. Does it care at all?

Thank you for your (hopefully forthcoming) support.
-- 
Kristoffer Eriksson, Peridot Konsult AB, Hagagatan 6, S-703 40 Oerebro, Sweden
Phone: +46 19-13 03 60  !  e-mail: ske at pkmab.se
Fax:   +46 19-11 51 03  !  or ...!{uunet,mcvax}!sunic.sunet.se!kullmar!pkmab!ske