>>>>> "CH" == Charles M Hannum <mycroft@ai.mit.edu> writes:

CH> If you obey these semantics, and the driver is coded correctly, then
CH> you never need `dial out' devices.  A program waiting for a `dial in'
CH> (e.g. getty) will wait in open() for carrier, and meanwhile a program
CH> can `dial out' by doing what I outlined above.

...but you still need some smarts in the `dial in' program.  It will
wake up when the dial-out program establishes {fake, real} carrier, so
it needs to know things like how to find UUCP-style lock files and honor
them by ignoring the serial line until it can acquire the lock file.
Likewise, dial-out programs must obtain the lock before opening and
manipulating the serial line.

==John