ch61.htm

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

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	<TR ALIGN="LEFT" rowspan="1">

		<TD WIDTH="127" ALIGN="LEFT">Close Window</TD>

		<TD ALIGN="LEFT">Closes the current Document View window. If you have only one window open, the entire

			application exits. Also available on the File menu.</TD>

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</TABLE>

When removing an extra window, such as an extra Browser window, remember to delete

or close the window. If you choose the Destroy option in your window manager, all

active sessions are destroyed.</P>

<P>The cursor in Mosaic or Netscape is generally a standard short arrow pointing

slightly to the left of 12 o'clock. The cursor changes its configuration depending

on where you are in the Document View window. It is the arrow configuration unless

it is pointing to a hyperlink. When the cursor rests on a hyperlink, it changes to

a small hand icon pointing to the left. When the cursor changes its configuration,

the hyperlink's URL is displayed in the information line. This URL tells you what

will be retrieved if you select the hyperlink. It also might tell you the format

of the document.

<CENTER>

<H3><A NAME="Heading36<FONT COLOR="#000077">Setting Up SLIP Connections</FONT></H3>

</CENTER>

<P>This section really belongs in a chapter by itself, but it's here because you

are most likely to run into these types of problems when trying to use your browser.

Setting up a SLIP connection is necessary if you are not already on the Internet.

To get a dialup SLIP connection, you have to use the /sbin/dip program. The dip stands

for Dialup Internet Protocol. For a dedicated connection, you should use the slattach

program.</P>

<P>If you are already connected to the Internet through another means, skip this

section entirely.

<CENTER>

<H4><A NAME="Heading37<FONT COLOR="#000077">dip</FONT></H4>

</CENTER>

<P>The dip program uses a script file to connect you to a SLIP account. You need

a SLIP account to use Mosaic or Netscape if you are connected to the Internet with

a serial connection. Using dip with a <TT>-t</TT> option can also let you run in

interactive mode for debugging, but in most cases you use it with a script file.</P>

<P>A script file is basically a file that handles your login and setup for you. You

invoke <TT>/sbin/dip</TT> with the script name as an argument. A sample script file

to work with my Internet SLIP account is shown in Listing 61.1. Your Internet provider

should provide a script for you. If it does not provide a script, ask for one.</P>

<P>Let's look at the sample script file in Listing 61.1.

<CENTER>

<H3><A NAME="Heading38<FONT COLOR="#000077">Listing 61.1. A sample dip script

file.</FONT></H3>

</CENTER>

<PRE><FONT COLOR="#0066FF">

main:

#

# Get the local and remote names for the network

#

get $remote remote

#

#

#

default

get $mtu 1500

port cua1

speed 38400

modem HAYES

flush

reset

send +++

sleep 1

send ate1v1m1q0\r

wait OK 2

if $errlvl != 0 goto error

send atdt5551212\r

if $errlvl != 0 goto error

# wait CONNECT 60

login:

sleep 3

wait login: 30

if $errlvl != 0 goto error

send johndoe\r

wait ord: 5

send  doa+sol!\r

wait TERM 10

send  dumb\r

wait $ 10

send dslip\r

wait Your 10

#

# get $remote remote

#

get $local remote

#

# Ask for the remote site's IP address interactively from the user

#

get $remote ask

# cannot do this dec $remote

done:

print LOCAL address is $local

print CONNECTED to $remote

print GATEWAY address $remote

default

mode CSLIP

goto exit

error:

        print SLIP to $remote failed

exit:

</FONT></PRE>

<P>Listing 61.1 shows how to access an Internet service provider via a dialup SLIP

account. This script gives you an example of how to log into the remote system and

get your local address, and it even asks you for the remote IP address.</P>

<P>Normally, you run the SLIP script as root. You can set the permissions on the

files in <TT>/etc/dip</TT> for all user access and not have to run as root. For debugging

purposes, the <TT>-v</TT> option echoes all the script lines as they are executed.

The <TT>echo on</TT> and <TT>echo off</TT> commands in script files turn the echoing

on or off while executing. The <TT>-v</TT> option is like having the <TT>echo on</TT>

command set as the first line in the script file.</P>

<P>The modem command in the scripts for dip supports only the <TT>HAYES</TT> parameter.

You can set the speed with the speed command. For other parameters of your modem,

use the Hayes command set. For example, <TT>ate1v1m1q0\r</TT> sends the accompanying

string to the modem to initialize it.</P>

<P>You can send output to the modem (and remote host) with the <TT>send</TT> command.

To wait for a specific string, use the <TT>wait</TT> command with part of the string

you are waiting for. Beware, though, that if the string you are waiting for never

appears, you can hang forever. The <TT>sleep</TT> command simply pauses the shell

execution for the specified number of seconds. All variables for dip must be lowercase

and preceded with a dollar sign. The dip program recognizes the following special

variables:</P>

<PRE><FONT COLOR="#0066FF">$remote for remote host name

$rmtip         for remote host IP address

$local for local host name

$locip         for local host IP address

$mtu   contains the MTU value for the connection.

&#194; You get this value from your internet provider.

</FONT></PRE>

<P>The <TT>get</TT> command is dip's way of setting a variable. The following line

requests the name of the remote host from the user. The <TT>ask</TT> parameter tells

<TT>dip</TT> to prompt the user for the input.</P>

<PRE><FONT COLOR="#0066FF">get $remote ask

</FONT></PRE>

<P>The local address for this script is derived when you log into your service provider.

The remote host prints a string of the form <TT>Your IP address is </TT>zzz.yyy.xxx.www.

So the script waits for the <TT>Your</TT> string and then gets the last word on the

line. Some SLIP service providers assign you a different address every time you log

in, so you have to do this. The way to do this is as follows:</P>

<PRE><FONT COLOR="#0066FF">#

# Get local address from this string.

#

wait Your 10

get $local remote

</FONT></PRE>

<P>The <TT>default</TT> command tells dip to route all default message traffic points

to the SLIP link. The <TT>default</TT> command should be executed just before the

<TT>mode</TT> command.</P>

<P>The <TT>mode</TT> command recognizes either <TT>SLIP</TT> or <TT>CSLIP</TT> as

a parameter. CSLIP is the compressed SLIP mode. If all goes well, the dip program

goes into daemon mode. The dip program executes the ifconfig program to automatically

configure your interface as a point-to-point link.</P>

<P>Finally, to kill an existing dip process, you can use <TT>/sbin/dip</TT> with

the <TT>-k</TT> option. You should do this when you turn off your machine or log

out to free up your phone line.



<DL>

	<DT></DT>

</DL>





<DL>

	<DD>

<HR>

<A NAME="Heading39<FONT COLOR="#000077"><B>NOTE:</B> </FONT>Read Chapter 43,

	&quot;Networking,&quot; to set your <TT>/etc/hosts</TT> file. Also, if you are not

	familiar with the <TT>ifconfig</TT> and <TT>traceroute</TT> commands, read the man

	pages for them. The ifconfig program configures and maintains kernel resident network

	interfaces. The <TT>traceroute</TT> command is useful in tracking messages as they

	come and go from your machine on the SLIP link. It is an invaluable tool for debugging.

	

<HR>



</DL>



<CENTER>

<H4><A NAME="Heading40<FONT COLOR="#000077">slattach</FONT></H4>

</CENTER>

<P>The <TT>slattach</TT> file is used to connect on a dedicated line to a remote

server. If your modem is on <TT>/dev/cua2</TT>, the command to configure a CSLIP

connection is run as root:</P>

<PRE><FONT COLOR="#0066FF"># slattach /dev/cua2 &amp;

</FONT></PRE>

<P>You can put this in your <TT>rc.inet</TT> files if you like. If your service provider

does not support CSLIP, you can use the <TT>-p</TT> slip option to get the uncompressed

SLIP mode. Just make sure that you run the same mode as your service provider.</P>

<P>Then, you execute the following commands:</P>

<PRE><FONT COLOR="#0066FF"># ifconfig sl0 localhost pointtopoint myrichISP

# route add myrichISP

# route add default gw myrichISP

</FONT></PRE>

<P>The first command connects you as a point-to-point to a SLIP connection. (The

<TT>sl0</TT> is s ell zero.) The next two commands add the node <TT>myrichISP</TT>

(the Internet service provider) as the default route.</P>

<P>To kill this connection, you must issue the following commands:</P>

<PRE><FONT COLOR="#0066FF"># route del default

# route del myrichISP

# ifconfig sl0 down

# kill -9 (slAttachPID)

</FONT></PRE>

<P>In this case, <TT>slAttachPID</TT> is the process ID of the slattach process.

<CENTER>

<H3><A NAME="Heading41<FONT COLOR="#000077">Summary</FONT></H3>

</CENTER>

<P>If you can use Netscape, you can use just about any other browser. All browsers

are based on the same basic principles of retrieving and displaying a file by checking

the type of data in it. After you know how to navigate using URLs, surfing the Net

becomes a task of learning how to use the special keys for your browser to help you

customize its functions to best suit your needs.</P>

<P>The following items were covered in this chapter:



<UL>

	<LI>Where to get Netscape for Linux, which versions to use, and how to debug common

	problems in Mosaic.

	<P>

	<LI>How to install Netscape on your machine after you get the distribution via FTP.

	<P>

	<LI>What alternatives you have to Netscape as far as browsers are concerned: Mosaic

	or Lynx, to name two.

	<P>

	<LI>A brief introduction to connecting your Linux node via SLIP to an Internet service

	provider.

</UL>



<P>Happy surfin'.









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