3B2/300 uucp ports & Permissions

[Duncan McEwan]

We have two AT&T 3B2/300s with SVR2.0 which are directly connected via
UUCP. One of the systems is also connected to a Pyramid 90x via a Micom
switch. The direct link between 3B2s uses uugetty at both ends to
provide a bi-directional link, but the link to the Micom switch is
outgoing only, and so the tty port must be turned off.

The problem is that the outgoing link to the Micom will only work
through the contty port, and not tty11 for example, whereas the
bidirectional direct link will successfully work through any port.

Testing was done using cu, which would only connect through to the Micom
via tty11 after a shutdown, but even then would not send any data.
Subsequent tries would result in the message CAN'T ACCESS DEVICE.
Swapping the direct link (which was on contty) with the Micom line
(which was on tty11) resulted in both links working well.

I suspect that the explanation is related to the difference between
uugetty and having a line turned off. I did try playing around with
/etc/gettydefs but to no avail. Although the system is now working
reasonably well I would be interested to know why it was not. Any ideas?


This second part is not a request for information, but more of a
warning, and help for those who may be wondering why their machines will
not communicate.

Concerning the 3B2/300s which are directly connected via UUCP, the Basic
Networking Utilities documentation specifies that in the Permissions
file, the MACHINE and LOGNAME entries may be combined into a single
entry. If this is done, neither machine can contact the other, the error
being Remote Reject After Login. It may be significant that the
permissions have been specified as relaxed as possible, i.e. so that
each machine has total access to the other. Splitting the Permissions
entries apart results in successful communication.


Ray Brownrigg
Applied Mathematics Division
DSIR (Department of Scientific and Industrial Research)
Wellington
New Zealand

UUCP: ...!alberta!calgary!mcewan (U of Calgary)
or ...!seismo!munnari!natmlab!dsir (Sydney, Australia, which
doesn't get mod.micro.att)
or ...!seismo!munnari!vuw90x!ray (Victoria University of
Wellington, New Zealand, which
doesn't either)

[Edward C. Bennett]

All this raises the more useful question:

1. Can the 3B2 control its outgoing DTR signal?

2. Can a tty port be opened without the incoming CD signal
being high?

--
Edward C. Bennett

UUCP: ihnp4!cbosgd!ukma!ukecc!edward

Kentucky: The state that is being dragged, kicking and screaming,
into the 20th century.

"Goodnight M.A."

[Brandon Allbery]

Expires:

Quoted from <4...@ukecc.UUCP> ["Re: 3B2/300 uucp ports & Permissions"], by edw...@ukecc.UUCP (Edward C. Bennett)...
+---------------

| All this raises the more useful question:
|
| 1. Can the 3B2 control its outgoing DTR signal?

+---------------

$ stty 0 > /dev/ttyxx # turn off DTR
$ # turning it on is more difficult, you have to open the port without
$ # DCD and ioctl() the baud rate to non-zero (see below)

+---------------

| 2. Can a tty port be opened without the incoming CD signal
| being high?

+---------------

#include <fcntl.h>
#include <termio.h>
#include <sys/ioctl.h>

#define TTY "/dev/ttyxx"

main() {
int fd;
struct termio ttydat;

if ((fd = open(TTY, O_RDONLY|O_NDELAY)) < 0)
exit(1);
ioctl(fd, TCGETA, &ttydat);
ttydat.c_cflag &= ~CBAUD;
ttydat.c_cflag |= Bmybaud; /* substitute your baud rate */
ioctl(fd, TCSETA, &ttydat);
exit(0);
}

The above program uses the fact that you can open for O_NDELAY a tty despite
neither DTR nor DCD being asserted; you can't read or write, but you CAN
ioctl. These are tested under System III (I have a much more complex version
of the above C program, run as ``dtr +tty22'' or similar, ``+'' for on, ``-''
for off), but should work under sys5 because the tty structure and code hasn't
changed (modulo sxt's).

If you want my ``dtr'' program, let me know.

--Brandon
--
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(ncoast!tdi2!root for business) 6615 Center St. #A1-105, Mentor, OH 44060-4101
Phone: +01 216 974 9210 CIS 74106,1032 MCI MAIL BALLBERY (part-time)
PC UNIX/UNIX PC - which do you like best? See <11...@ncoast.UUCP> in net.unix.

[Ron Thompson]

>
> All this raises the more useful question:
>
> 1. Can the 3B2 control its outgoing DTR signal?

Let's see if I can get this right-
The open raises it, setting BAUD to 0 lowers DTR. It can't be
made to go high again without a close and successive open.

>
> 2. Can a tty port be opened without the incoming CD signal
> being high?

I think the flag NODELAY (spelling), for the open does this.
--
Ron Thompson AT&T Information Systems Customer Programming
(404) 982-4217 Atlanta, Georgia Services Center
..{ihnp4,akgua}!cpsc53!rt (Opinions expressed are mine alone.)