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From: rickert@mp.cs.niu.edu (Neil Rickert)
Newsgroups: comp.mail.sendmail
Subject: Re: what is net hang?
Message-ID: <1991Jun20.151726.24714@mp.cs.niu.edu>
Date: 20 Jun 91 15:17:26 GMT
References: <MNL.91Jun20142856@mnlsun.idtsun.e-technik.th-darmstadt.de>
Organization: Northern Illinois University
Lines: 29

In article <MNL.91Jun20142856@mnlsun.idtsun.e-technik.th-darmstadt.de> mnl@idtsun.e-technik.th-darmstadt.de (Michael N. Lipp) writes:
>Jun 20 02:58:01 marlowe sendmail[9569]: AA09569: SYSERR: net hang reading from spade.dtro.e-technik.th-darmstadt.de: Connection timed out during collect with spade.dtro.e-technik.th-darmstadt.de
>
>Can anybody tell me what "net hang" is? The two are on the same

  This usually occurs when there is some miscommunication and both ends of
the SMTP connection are reading and waiting for the other end to
send something.

>ethernet (and spade being /usr-NFS-client couldn`t run without marlowe
>anyway). So the net should work. When tested by hand, mailing on the
>machines works flawlessly. Looking at the dates, someone suggested
>that it is "batch -m" that sends the offending messages. But what
>could batch do when execing sendmail that makes sendmail fail that way?

  As a rough guess, based on its name, perhaps "batch" is sending a "batch"
of SMTP commands.

  As defined, SMTP is a dialogue, with a response for each SMTP command.
After sending a command, you are supposed to wait for the response before
sending anything more.  The design of sendmail depends on this behavior.
Failure to observe it can lead to exactly this kind of net hang.


-- 
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  Neil W. Rickert, Computer Science               <rickert@cs.niu.edu>
  Northern Illinois Univ.
  DeKalb, IL 60115                                   +1-815-753-6940