From: bender@oobleck (Duke of Canterbury)
Newsgroups: comp.dcom.modems
Subject: Re: Dialin access to Sun 4/110
Date: 8 Nov 1992 17:43:53 GMT
Organization: SPARK's R US
Reply-To: bender@oobleck.eng.sun.com
NNTP-Posting-Host: oobleck
X-Newsreader: Tin 1.1 PL3

ivory@e7sa.crd.ge.com (John Ivory) writes:
: Okay, I give up.  What are the steps involved in getting my Sun 4/110
: running 4.1.2 SunOS, with a V.32 BIS Zoom modem attatched to /dev/ttya
: to accept incoming calls and allow users to login?
:
: After I make the seemingly correct edits to /etc/ttytab, as well as
: edits to /etc/uucp/Devices (suggested in the pcomm 'Q_and_A' doc),
: and reboot, attempts to dial out on the modem fail because I can no
: longer open that device, dialin's don't seem to connect, and the RD/SD
: lights of the modem just blink busily.  What gives?!

John,
  You should check a few things:

    - your modem must keep CD low when it's not connected
	to another modem
    - your modem must drop the connection to the other modem
	when DTR from the Sun drops
    - /dev/ttya must have softcarrier disabled (do a man ttysoftcar)

  It sounds like the Sun is sending "login:" to your modem, which is echoing
it back to the Sun, which the Sun thinks is a user name, so the Sun sends
"Password:" to the modem, which the modem echos back to the Sun, which
thinks it's a password, which is (probably :-) an invalid username/password
combination, so the Sun sends "Login incorrect:" to your modem followed by
another "login:", your modem echos that stuff back to the Sun and the cycle
starts over again.

  The way the serial port login stuff on SunOS 4.X works is that getty does
an open() on the serial port, but the open() blocks in the zs driver (that's
the driver responsible for /dev/ttya and /dev/ttyb) if the CD line from the
modem is not asserted, i.e. the modem isn't connected to another modem.  At
this point, you can use a program like tip or pcomm to dial OUT on the modem
by opening the /dev/cua0 port, which is really just another name for
/dev/ttya but with the high bit set in the device's minor number which tells
the zs driver NOT to wait for CD to be high from the modem on an open().
Once you finish using the modem for dial-out and close() the /dev/cua0
device, if a call comes in and your modem answers it, the modem's CD line
will be asserted, which will continue with the open() that getty did a while
back, but which was up until this time blocking (waiting) in the zs driver.
getty will generate the first "login:" message and then hand off the username
to login to take care of the rest.  Once the incoming caller logs out, the CD
line from the modem will drop, abd init will shortly fire up another getty,
which will block once again in the open(), waiting for CD to be asserted on
the next dial-in connection.

  Sun (any other UNIXes) have this strange thing called softcarrier, which
is basically a flag that tells a serial port driver to IGNORE the state of
the CD line from your modem, no matter what the hardware says it's state is,
and instead just pretend that CD is always ACTIVE.  A side effect of this is
that if sotfcarrier is set on a serial port, and you want to use the port
for dial-in modem connections, whenever getty starts up and does an open()
to the port, the open() will immediately succeede (sp?) and getty will spit
out a "login:" message, without waiting for CD from the modem to be asserted.
I have softcarrier enabled on several of the serial ports that I have
connected to terminals, X10 controllers and other stuff that either doesn't
support a CD line, or I haven't been bothered to wire up a calbe with CD
passing all the way through from the device to the Sun serial port.

  I know this is long winded and you did specify e-mail, but I thought that
some other people in this group might run into the same problems getting a
dial-in and dial-out modem going, so I posted rather than e-mailed.

mike

--
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 mike bender  DOD# 007  for sale: NX-650 & VT110 Shadow	415-863-8913 (home)
	cheap advertising -->	$2500/obo    $2500/obo
 bender@oobleck.eng.sun.com    nothin' witty here	415-336-6353 (work)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~