<sect1 id="server-usage-overview">

    <title>Overview</title>

    <para>
        The infrastructure described in this chapter uses the
        client/server model to provide a public mail service through
        the telephone line. In this configuration, we (the poeple
        building the infrastructure) provide the information you (the
        person using the infrastructure) need to know in order to
        establish a dial-up connection from the client computer to the
        server computer through the telephone line.
    </para>

    <para>
        The infrastructure described in this chapter is made available
        to you free of charge, however, you should know that
        maintaining it costs both money and time. For example, for
        each hour the server computer is on production there is an
        electrical consume that need to be paid every month.
        Likewise, each call that you establish from the client
        computer to the server computer will cost you money, based on
        the location you made the call from and the time you spend
        connected.
    </para>

    <para>
        In this manual, by dial-up connection we mean the action of
        dialing-up a server computer from a client computer through a
        Modem attached to the telephone line. In this infrastructure,
        dial-up connections are always established from the client
        computer to the server computer and never the other way
        around.  The main purpose of a client computer to establish a
        dial-up connection with the server computer will be using one
        or more Internet services provided in the server computer.
    </para>

    <para>
        In order for the server computer to answer telephone calls, it
        is required to install a Modem device in it (see <xref
        linkend="server-install-modem" />). Once the Modem device has
        been installed, you need to install and configure both
        <application>mgetty</application> and
        <application>pppd</application> programs.  The
        <application>mgetty</application> program must be run by
        <systemitem class="daemon">init</systemitem> daemon in order
        to take control over the Modem device. By default, inside
        &TCD; (release 5.5), mgetty isn't configured to start with
        <systemitem class="daemon">init</systemitem> daemon so you
        need to do it yourself (see ...). Later, for attending
        connection requests, you need to configure mgetty to use the
        <application>pppd</application> program, so the Point-to-Point
        Protocol (PPP) can be talked and IP packages can be
        interchanged between the client computer and the server
        computer. Later, you need to configure
        <application>pppd</application> to adjust it to your needs
        (see ...). 
    </para>
    
    <para>
        Once you've configured both <application>mgetty</application>
        and <application>pppd</application> programs, the server
        computer should be ready to attend incoming calls.  The
        remaining of this chapter describes the way incoming calls are
        attended by the server computer once they have arrived to its
        Modem device.
    </para>

</sect1>