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From: wescott@sauron.UUCP
Newsgroups: comp.sources.wanted,comp.unix.wizards,comp.unix.questions
Subject: Re: UUCP Port Turnaround
Message-ID: <824@sauron.Columbia.NCR.COM>
Date: Tue, 10-Feb-87 18:27:42 EST
Article-I.D.: sauron.824
Posted: Tue Feb 10 18:27:42 1987
Date-Received: Thu, 12-Feb-87 23:01:15 EST
References: <171@ndmath.UUCP> <4090@nsc.nsc.com> <166@piaget.UUCP>
Sender: news@sauron.Columbia.NCR.COM
Reply-To: wescott@sauron.UUCP (Mike Wescott)
Organization: Advanced Systems Development, NCR Corp., Columbia, SC
Lines: 29
Keywords: uucp
Xref: utgpu comp.sources.wanted:484 comp.unix.wizards:907 comp.unix.questions:990

In article <166@piaget.UUCP> jc@piaget.UUCP (John Cornelius, System Manager) writes:
> In article <4090@nsc.nsc.com> jon@nsc.UUCP (Jon Ryshpan) writes:
>  >Does anyone know a simple method to "turn a port around" so as to
>  >make an outgoing call on a port which is usually used for incoming
>  >connections? ...
> HDB uucp permits this.  A separate getty (uugetty) is fired up
> for such lines.  Uugetty locks the port with a lock file.  I do
> not know the mechanism for making uugetty unconcious but I
> presume that a signal is used.

The HDB uugetty waits until the line is active before checking for a lock.

The line is active when the open completes (i.e. Carrier Detect is on) or,
if uugetty is invoked with a '-r' option, when the first character is received.

uugetty checks the lock file for the line and if the file is not present or
if it contains an old pid, uugetty sets a new lock and continues much like
/etc/getty.  Note that nobody removes this lock file until a new uugetty
or uucico finds that the pid in it is no longer valid.

If a valid lock is present, then uugetty loops sleeping and rechecking the
lock.  When the locking process has terminated, uugetty exits and is respawned
by init.

The HDB uugetty will not work on 4.? machines because of the mechanism used
to check locks.
-- 
	-Mike Wescott
	 ncrcae!wescott