Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!mcgill-vision!bloom-beacon!snorkelwacker!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!samsung!umich!ox.com!oxtrap!oxtrap!time From: time@oxtrap.aa.ox.com (Tim Endres) Newsgroups: comp.unix.aux Subject: Re: modems, getty Message-ID: Date: 6 Feb 90 22:13:39 GMT References: <613@cspi.cspi.com> <194@brain.UUCP> Sender: time@oxtrap.aa.ox.com (Tim Endres) Reply-To: time@oxtrap.UUCP Organization: Oxtrap - Ann Arbor, MI Lines: 36 In-Reply-To: root@brain.UUCP's message of 1 Feb 90 21:13:15 GMT This topic needs a little more discussion. The way the distribution getty for A/UX works is as follows: . getty is invoked by init with parameters from inittab. . getty resolves the parameters and gets more from /etc/gettydefs. . getty call open() on the serial line (/dev/.....). This asserts the DTR line on the port. . open() BLOCKS until the CARRIER DETECT comes high. This is a result of using "modem" control on the device which can be specified with "stty modem". This also causes Kermit to hang if the modem is not yet connected, which is why "stty -modem" exists. . When the CARRIER DETECT line is asserted, the open() call succeeds and getty proceeds with the login: prompt. Now, if you either (1) don't have modem control set [a gettydefs parm] -or- (2) your cable does not pass the CD line properly, then getty's open() succeeds immediately, and the modem gets the *command* login: which of course it does not like so it says "ERROR" which, of course, gets a "password:" from the spawned login process. Finally, the login attempt of ERROR with password ERROR fails, and the cycle repeats itself causing the "blinking lights" problem many people have. Another problem exists when the modem (as many HAYES like to do) asserts CD all the time on its own. This is provided for brain dead applications that can not deal with the fact that CD is low. This is usually a DIP switch setting on the Hayes. Finally, if you can not get getty to block on CD, then you can use the technique of putting the modem into "quiet" mode, thus avoiding the input from the modem (i.e. RING, RING, CONNECT). This is not an optimal solution, but it gets the job done most of the time. Also, drop of DTR should drop a connection and should reset the modem if possible. Further, calls should not be accepted with DTR low. [Cathy, I tried e-mail, but it bounced.] tim.