Re: Bug#10918: xringd: after the first ring my RD SD led are on (fwd)

Richard B. Johnson (
Thu, 10 Jul 1997 21:51:36 -0400 (EDT)

On Thu, 10 Jul 1997, Andrea Arcangeli wrote:
> #include <stdio.h>
> #include <fcntl.h>
> void main(void) {
> int fd;
> printf("I am attempting to open modem device /dev/modem\n");
> if((fd = open("/dev/modem",O_RDONLY))<0) {
> printf("Modem not opened\n");
> exit(-1);
> }
> printf("Modem opened successfully\n");
> getchar();
> }
You need to set the fd to not echo characters! By default, the driver
presumes that someone is going to log in via a ttySn and they expect to
see what they typed echoed until /bin/login gets control and turns off
echo when you type a password.

When you open the "modem", the modem will detect DSR/CTS and send an
"Ok", this gets echoed back to the modem, which echoes the same thing
etc OKOKOKOKOK <forever>

If you need more help, contact me via private I
will give you working snippets of code that do the necessary stuff. I
have a "homemade" dial-back program that uses all the primatives you need.
I use this every night to get my work-system to call me back so I don't
run up a long-distance phone bill.

Richard B. Johnson
Analogic Corporation
Email :,
Penguin : Linux version 2.1.44 on an i586 machine (66.15 BogoMips).
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