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Path: utzoo!mnetor!seismo!vrdxhq!BMS-AT!stuart
From: stuart@BMS-AT.UUCP (Stuart D. Gathman)
Newsgroups: net.unix
Subject: Re: Getting Modems to work under Ultrix Version 1.2
Message-ID: <223@BMS-AT.UUCP>
Date: Sun, 28-Sep-86 14:58:54 EDT
Article-I.D.: BMS-AT.223
Posted: Sun Sep 28 14:58:54 1986
Date-Received: Wed, 1-Oct-86 00:19:15 EDT
References: <107@mit-prep.ARPA>
Organization: Business Management Systems, Inc., Fairfax, VA
Lines: 18
Summary: Open waiting for modems.

In article <107@mit-prep.ARPA>, shanzer@mit-prep.ARPA (Mike Shanzer) writes:

> 	I have a question, I am trying to open a modem for writting under
> Ultrix V1.2, how ever when I try to do this the open hangs. DOes any
> one know why it does this and how I can fix it? 

The open is waiting for the modem to connect (i.e. for CD to turn on).
If this is a Hayes type auto-dial modem, you need to open it in a mode
which does not wait for 'CD'.  On some systems, this is a special device
file which has no modem control (this emulates older autodialers which
required two ports: one for dialing and one for communications).  On others,
(and this *should* work on all systems, but alas there are always bugs)
you should give the O_NDELAY parameter on your open.  This will ignore
the CD lead while you give dialing commands.  Ideally, another process
should be waiting on an open without O_NDELAY, i.e. fork() to do the
dialing.
-- 
Stuart D. Gathman	<..!seismo!{vrdxhq|dgis}!BMS-AT!stuart>