Problems using rn over a telnet connection

[Kevin Darcy]

In article <1991May24.212235.8187 at otsc.eds.com> snyde_sl at tsca02.uucp (Steve Snyder) writes:
>Our site recently established a newsfeed.  We are running C news (last
>patch date is 24-Mar-91) and rn (last patch date is 01-Jan-91, # 54)
>on an Apollo DN3000 under Domain/OS SR10.2 (sys 5.3 environment).
>The ASCII terminals we have are connected to Black Box terminal
>servers.
>
>The problem we are having concerns using rn over a telnet or rlogin
>connection to the news server.  It seems that regardless of what type 
>of terminal (VT100, VT320, PC, SUN SPARC2, HP9000/380, or even another 
>Apollo bitmap display) I use to telnet to the news server, this 
>problem occurs.  The problem is that rn repeatedly displays the 
>first '--read now? [npq]' prompt (beeping every time) as shown below:
>
> [example given]
>
>So I just have to quit and get out of rn.  [further details]
>
>Any ideas why rn responds this way over a telnet connection, or 
>possible solutions to this problem?  I've run out of ideas.  I posted 
>this previously to news.software.b and news.newusers.questions but got
>no responses.

We've seen identical behavior from rn and trn over AT&T Starlan connections
on 3B2's. My guess is that the pty driver used by your telnetd is based 
on STREAMS, and the rn/trn code is known to not handle STREAMS-based tty 
drivers quite correctly in O_NDELAY mode.

Specifically, the code doesn't respect the following critical distinction 
(this is a quote from the read(2) section of a vendor manual):

	When attempting to read a file associated with a tty has no
	data currently available:

		If O_NDELAY is set, the read will return 0.

		[...]

	When attempting to read a file associated with a _stream_ that has no
	data currently available:

		If O_NDELAY is set, the read will return a -1 and set errno to
		EAGAIN.

We have a local hack that works around this problem. I can send it to anyone
who is interested.

Followups to news.software.b and/or comp.unix.programmer.

>Steve Snyder             | You've got to know when to code 'em,
>Electronic Data Systems  | know when to modem, know when to load 'em,
>snyde_sl at otsc.eds.com    | and know when to run.
>uunet!tsca02!snyde_sl    |                        --Anonymous

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