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<!DOCTYPE LINUXDOC SYSTEM>
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<ARTICLE>
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<title>call-back mini HOWTO
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<author>by Pawel Skonecki, <tt><htmlurl url="mailto:stona@fizyka.umcs.lublin.pl" name="stona@fizyka.umcs.lublin.pl"></tt>
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<date>v1.1a, June 2000</date>
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<abstract>
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This document describes how to set up call-back by using the Linux
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system and modem. I would like to thank Anna for her patience.
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</abstract>
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<TOC>
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<SECT>Introduction
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<SECT1>OPINION
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<P>
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I'll will be waiting for all opinions about this document. I have tried
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to gather information as complete as possible. Tell me when your find
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any mistakes. I'll be grateful to people who will send me any suggestions
|
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or corrections. Their contributions will make this document better.
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I don't mind answering your questions but I'd rather you read the
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whole article first.
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</SECT1>
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<SECT1>PUBLISHING
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<P>
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This document can by published under the conditions of Linux Documentation
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Project. Get in touch with the author if you can't get this license.
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This document is free.
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</SECT1>
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</SECT>
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<SECT>Procedure
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<SECT1>PART I: Net at home ?
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<P>
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Most of us use the Internet in a place of work. However we offen need
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the net at home or outside the place of work. It may be possible that
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the work from home is cheaper then from a company building. I think
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that the best solution is to install call-back software on the Linux
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server. Call-back makes it possible to re-call index number at the
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cost of the company. I'll try to present how it works. An entitled
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person calls modem is varied for the first time in Linux server. Then
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on the user's side the "hang up modem" is switched on. At the same
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time Linux calls the user. User is verified again. We have connection
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and the server is charged. The user pays only for the initiation of
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connection. The double verification and extra options in the call-back
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program unable the unsuitable persons to charge our bill. We can restrict
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the access to the connection only to corporation network or Internet.
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Call-back is very flexible. Below, I'll try to present the configuration
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of a call-back server on Linux system and I'll show you how to set
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up your computer for re-calling the connection.
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</SECT1>
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<SECT1>PART II: The first steps with modem.
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<P>
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The administrators prefer different modem but while buying a modem
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we should remember about certain rules:
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<itemize>
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<item>Don't buy the Win-Modem because it doesn't work with Linux
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<item>The external modem works faster than the modem which is inside your
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computer
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<item>The internal modem with ISA slot is better then the are with PCI
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slot (you can use your PCI slot for something different)
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<item>Don't use Plug&Play modem. If you have it set off, Plug&Play options
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and set up modem on free com (read Plug&Play-HOWTO).
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</itemize>
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<P>
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When we have the suitable modem we have to set it up in our system.
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We have to check on which com our modem is. Then we have to make a
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symbolic link to this hardware and /dev/modem. For example, if we
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have the modem for the 2nd com we write:
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<VERB>
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ln -s /dev/cua1 /dev/modem
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</VERB>
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We check it
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<VERB>
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lrwxrwxrwx 1 root uucp 9 Sep 19 19:10 /dev/modem -> /dev/cua1
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</VERB>
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If we have the modem on different com we have to remember that
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<VERB>
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/dev/cua0 is com1
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/dev/cua1 is com2
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/dev/cua2 is com3
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/dev/cua3 is com4
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</VERB>
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For new kernels:
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<VERB>
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/dev/ttyS0 is com1
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/dev/ttyS1 is com2
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/dev/ttyS2 is com3
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/dev/ttyS3 is com4
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</VERB>
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Now, we check our configuration using the program minicom.
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</SECT1>
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<SECT1>PART III Call Linux
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<P>
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The first step to make the call-back on Linux accessible is to set
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up a suitable parameter in kernel. Then we check whether our kernel
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serves the protocol ppp. If you don't have ppp in your kernel or in
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module you will have to compile your kernel and add ppp. You will
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find more information in Kernel-HOWTO. OK. We have a good kernel.
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Now, we have to set up software to our system. The call-back program
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is a part of mgetty-sendfax and ppp. You will find it all in your
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distribution. Because call-back system we have double verification
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and we create a user who will be running ppp on the side of server.
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<VERB>
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pppuser:klkIOM89mn65H:230:PPP Dialin:/home/pppuser:/etc/ppp/ppplogin
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</VERB>
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Then change the password. We have to add information abut password in
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the file <TT>/etc/ppp/pap-secrets</TT> (more in man pppd)
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<VERB>
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pppuser * password_for_pppuser *
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</VERB>
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This user doesn't have a usual shell but a file <TT>/etc/ppp/ppplogin</TT>.
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We have to make it ourselves. for example <TT>vi /etc/ppp/ppplogin</TT> and
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we type:
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<VERB>
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#!/bin/sh
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exec /usr/sbin/pppd -detach 192.168.1.1:192.168.1.2
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</VERB>
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where the address 192.168.1.1 is the address of server with modem and
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the address 192.168.1.2 is the address which we assigned to our modem.
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We set up executable options for this file. Because we will use the
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ppp demon we have to set up the options for this demon. We edit file
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<TT>/etc/ppp/options</TT>:
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<VERB>
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netmask 255.255.255.0
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proxyarp
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lock
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crtscts
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modem
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</VERB>
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Proxyarp is the most important from the above options, because you
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can go to Internet by the modem in the server. The remaining options
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are used control your modem. Your user can work only in local network
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if you remove proxyarp option. You have to see PPP-HOWTO and man pppd
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for more information. We will set up our modem now. Our server must
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be ready to receive a connection after start. We edit file <TT>/etc/inittab</TT>
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and we add it's to modem on the 2en com.
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<VERB>
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s1:2345:respawn:/sbin/mgetty ttyS1 -D /dev/ttyS1 vt100
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</VERB>
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For the 1st com line looks as follows:
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<VERB>
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s0:2345:respawn:/sbin/mgetty ttyS1 -D /dev/ttyS1 vt100
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</VERB>
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We make <TT>init q</TT>. If we don't have information about any mistakes in
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logs we go to the next step. We come back to directory <TT>/etc/ppp</TT> and
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create <TT>options.ttyS1</TT> (for modem com1 <TT>options.ttyS0</TT>)
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<VERB>
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IP_local: IP_remote
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</VERB>
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for our net it will be
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<VERB>
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192.168.1.1:192.168.1.2
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</VERB>
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We have done a lot work so far. Now, we check the file
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<TT>/etc/mgetty+sendfax/login.config</TT>. The most important line is:
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<VERB>
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/AutoPPP/ - a_ppp /usr/sbin/pppd auth -chap +pap login detach kdebug 7 debug
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</VERB>
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The remaining lines can be marked <TT>#</TT>.
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<P>
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We have to set up suid for ppp demon, because pppuser has to run pppd
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and make interface work.
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<VERB>
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chmod u+s /usr/sbin/pppd
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</VERB>
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and its effect is:
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<VERB>
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-rwsr-xr-x 1 root root 106892 Jan 11 1999 /usr/sbin/pppd
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</VERB>
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I think that it is a good idea is to add it to cron becouse I had a
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problem after restart of my server pppd changed preference.
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Our server will work as router. We have to enable IP forwarding and
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we add this line for the file <tt>/etc/rc.d/rc.local</tt> :
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<VERB>
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echo "1" > /proc/sys/net/ipv4/ip_forward
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</VERB>
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If you are RedHat user you can change in <TT>/etc/sysconfig/network</TT> from
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<TT>FORWARD_IPV4=false</TT> to <TT>FORWARD_IPV4=true</TT>.
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<P>
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For verification we call to Linux. We use scripts for it. If we do this in
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MS Windows we mark options <tt>"call out a terminal after connection"</TT>.
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We login as pppuser with its password. I hope that all is OK.
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</SECT1>
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<SECT1>PART IV Linux calls us
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<P>
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We can already call our Linux. Now it's time Linux called us. It's
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not very diffucalt. We have to edit only two files. We create a file
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<TT>/etc/mgetty+sendfax/callback.conf</TT> and we leave it empty.
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<P>
|
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Then we have to ask our users for their phone number. It's time to
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write the numbers we have connected earlier. In order to do it we
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edit <TT>/etc/mgetty+sendfax/login.conf</TT> and add line:
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<VERB>
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call - - /usr/sbin/callback - S 123456
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</VERB>
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where call is a pseudo-user needed to initiate the connection. The
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line in the <TT>/etc/mgetty+sendfax/login.conf</TT> puts in motion the program
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calling the given number (in this case it's 123456). The same procedures
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can be applied to other users. I'll try to explain how it works. When
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we call a server. It asks us to give verification. We login as pseudo-user,
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in this case it calls. The script in our computer hangs up the modem.
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We wait and the connection is cut off. The program call-back starts
|
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working and recalls us. We verify ourselves again as pppuser with
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password. We combine the connection and interface ppp. That's all. The
|
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configuration of work-stations is very simple. When you have MS
|
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Windows, you have to install dial-up for your number. In the modem
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propriety we find " propriety--->extended---> extra options" where
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we write.
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<VERB>
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&c0s0=1
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</VERB>
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|
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We close the window and call. We log in according to the description
|
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given above. If we want to use Linux, we must refer to the script.
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It's difficult to give only one good script for our Linux. A good
|
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configuration of ppp in the system is of primary importance. (You
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can call it as pppuser through the scripts first).The scripts below
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were whiten by A. Gozdz. I suggest putting everything to catalogue.
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It is only my suggestion & you don't have to start the scripts here.
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Detailed information cocernig writing scripts on Linux can found in
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PPP-HOWTO.
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|
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<P>
|
||||
<BF>THESE SCRIPTS WORK WELL WITH SLACKWARE</BF>
|
||||
|
||||
<P>
|
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The configuration file of daemon ppp (an example for modem on com2)
|
||||
<TT>/etc/options</TT>
|
||||
|
||||
<VERB>
|
||||
|
||||
lock
|
||||
|
||||
defaultroute
|
||||
|
||||
noipdefault
|
||||
|
||||
modem
|
||||
|
||||
/dev/cua1
|
||||
|
||||
33600
|
||||
|
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crtscts
|
||||
|
||||
debug
|
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|
||||
passive
|
||||
|
||||
asyncmap 0
|
||||
|
||||
</VERB>
|
||||
|
||||
and the specific scripts
|
||||
|
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<itemize>
|
||||
|
||||
<item>the first named /etc/ppp/ppp-call
|
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|
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<VERB>
|
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#!/bin/bash
|
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|
||||
teksta="Connection failed"
|
||||
|
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tekstb="Probably, You will be connect"
|
||||
|
||||
# /sbin/setserial /dev/cua1 spd_vhi
|
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|
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killall -INT pppd 2>/dev/null
|
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|
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rm -f /var/lock/LCK* /var/run/ppp*.pid
|
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|
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(/usr/sbin/pppd -detach /dev/ttyS1 115200 \
|
||||
|
||||
connect "/usr/sbin/chat -v -f /etc/ppp/pppcallback" &) || \
|
||||
|
||||
(echo $teksta; ls marsss >/dev/null; exit 1)
|
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|
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echo $tekstb
|
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|
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exit 0
|
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</VERB>
|
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|
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<item>the second file called /etc/ppp/pppcallback
|
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|
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<VERB>
|
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TIMEOUT 60
|
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|
||||
ABORT 'ERROR'
|
||||
|
||||
ABORT 'BUSY'
|
||||
|
||||
ABORT 'NO ANSWER'
|
||||
|
||||
ABORT 'NO DIALTONE'
|
||||
|
||||
ABORT '\nVOICE\r'
|
||||
|
||||
ABORT '\nRINGING\r\n\r\nRINGING\r'
|
||||
|
||||
'' AT&FH0 <p>'OK-+++\c-OK' 'AT&C0S0=1'
|
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|
||||
TIMEOUT 75
|
||||
|
||||
OK ATDT123456
|
||||
|
||||
CONNECT ''
|
||||
|
||||
ogin:-ogin: ppp_pseudouser
|
||||
|
||||
'\nNO CARRIER\r' ''
|
||||
|
||||
TIMEOUT 180
|
||||
|
||||
'\nRING\r' AT&C1A
|
||||
|
||||
CONNECT ''
|
||||
|
||||
TIMEOUT 20
|
||||
|
||||
ogin:-ogin: pppuser
|
||||
|
||||
sword:-sword password_for_pppuser
|
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</VERB>
|
||||
|
||||
<item>You can ppp-call, now. :)
|
||||
|
||||
</itemize>
|
||||
|
||||
<P>
|
||||
<BF>THESE SCRIPTS WORK GOOD WITH LINUX RED HAT 6.x</BF>
|
||||
|
||||
<itemize>
|
||||
|
||||
<item>/etc/ppp/options
|
||||
|
||||
<VERB>
|
||||
lock
|
||||
|
||||
defaultroute
|
||||
|
||||
noipdefault
|
||||
|
||||
modem
|
||||
|
||||
33600
|
||||
|
||||
crtscts
|
||||
|
||||
debug
|
||||
|
||||
passive
|
||||
|
||||
asyncmap 0
|
||||
</VERB>
|
||||
|
||||
<item>/etc/ppp/pppcallback
|
||||
|
||||
<VERB>
|
||||
TIMEOUT 5
|
||||
|
||||
ABORT 'ERROR'
|
||||
|
||||
ABORT 'BUSY'
|
||||
|
||||
ABORT 'NO ANSWER'
|
||||
|
||||
ABORT 'NO DIALTONE'
|
||||
|
||||
ABORT '\nVOICE\r'
|
||||
|
||||
ABORT '\nRINGING\r\n\r\nRINGING\r'
|
||||
|
||||
'' AT&FH0 'OK-+++\c-OK' 'AT&C0S0=1'
|
||||
|
||||
TIMEOUT 40
|
||||
|
||||
OK ATDT5376443 CONNECT ''
|
||||
|
||||
ogin:-ogin: ppp-pseudo-user
|
||||
|
||||
'\nNO CARRIER\r' ''
|
||||
|
||||
TIMEOUT 180
|
||||
|
||||
'\nRING\r' AT&C1A
|
||||
|
||||
CONNECT ''
|
||||
|
||||
TIMEOUT 20
|
||||
|
||||
ogin:-ogin: pppuser
|
||||
|
||||
sword:-sword password_for_ppuser
|
||||
|
||||
</VERB>
|
||||
|
||||
<item>/usr/bin/ppp-call
|
||||
|
||||
<VERB>
|
||||
#!/bin/bash
|
||||
|
||||
teksta="Connection failed"
|
||||
|
||||
tekstb="Probably, You will be connect"
|
||||
|
||||
# /sbin/setserial /dev/cua1 spd_vhi
|
||||
|
||||
killall -INT pppd 2>/dev/null
|
||||
|
||||
rm -f /var/lock/LCK* /var/run/ppp*.pid
|
||||
|
||||
(/usr/sbin/pppd -detach call ppp_call &) || \
|
||||
|
||||
(echo $teksta; ls marsss >/dev/null; exit 1)
|
||||
|
||||
echo $tekstb
|
||||
|
||||
exit 0
|
||||
</VERB>
|
||||
|
||||
<item>You can run ppp-call, now. :)
|
||||
|
||||
</itemize>
|
||||
|
||||
<P>
|
||||
If you have M$ Windows you can use this script for conection. I don't
|
||||
test it (I use terminal) you can ask some more Adrian Debkowski
|
||||
(<htmlurl url="mailto:adrian@cr-media.pl" name="adrian@cr-media.pl">).
|
||||
|
||||
<VERB>
|
||||
proc main
|
||||
|
||||
delay 1
|
||||
|
||||
waitfor "ogin:"
|
||||
|
||||
transmit "call^M"
|
||||
|
||||
waitfor "RING"
|
||||
|
||||
transmit "ATA^M"
|
||||
|
||||
waitfor "CONNECT"
|
||||
|
||||
waitfor "ogin:"
|
||||
|
||||
transmit "pppuser^M"
|
||||
|
||||
waitfor "word:"
|
||||
|
||||
transmit "ppp^M"
|
||||
|
||||
endproc
|
||||
</VERB>
|
||||
|
||||
</SECT1>
|
||||
|
||||
<SECT1>PART V Summary
|
||||
|
||||
<P>
|
||||
The Configuration of call-back is not complicated. The most important
|
||||
thing is a proper arrangement of ppp server on Linux. I don't know
|
||||
a better way of setting up an access - server. The configuration presented
|
||||
above is a result of numerous attempts and it can be done in a different
|
||||
way. That's way I suggest reading all documents concerning this issue
|
||||
man pppd, NET4-HOWTO, PPP-HOWTO.
|
||||
|
||||
</SECT1>
|
||||
</SECT>
|
||||
|
||||
</ARTICLE>
|
||||
Loading…
Reference in New Issue