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<title>A Visual Packet Monitor LG #41</title>
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<H4>
"Linux Gazette...<I>making Linux just a little more fun!</I>"
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<H1><font color="maroon">A Visual Packet Monitor</font></H1>
<h4>By <a href="mailto: layers@marktwain.net">Larry Ayers</a></h4>
</center>
<P> <HR> <P>
<center><H3><font color="maroon">Introduction</font></h3></center>
<p>For the past few years I've used internal modems, but I still miss the
flickering lights on the first modem I ever used, an external unit which
seemed fast at the time. One of these lights indicated incoming data-packets
while another showed the outgoing. The advantages of these inobtrusive
lights were that they didn't occupy screen real-estate and they could be monitored
with peripheral vision.
<p>Recently Matthew Bevan released a new version of NetLED, a small utility
which monitors any of several interfaces such as PPP, SLIP, or ethernet using
the keyboard's light emitting diodes (LEDs). This is a great idea, since
these LEDs aren't particularly useful in their native state. I've never had
any use for the Caps Lock key, or its LED; I like to have that key generate
the Escape key key-code (easing VI mode-switching), which leaves its LED open
for alternate uses such as NetLED.
<p>NetLED is a tiny program (meant to be run as a daemon) which can be left
running even when a network interface is inactive. The command syntax is
simple:<br>
<p><kbd>netled [console] [interface]</kbd><br>
<p>As an example, I use it to monitor activity on a dial-in PPP
connection:<br>
<p><kbd>netled console ppp0</kbd><br>
<p>The <b>console</b> parameter, if just "console" is specified,
allows the LEDs to flash on all consoles, while <b>ppp0</b> tells the program
to monitor the first PPP device. Substitute <b>eth0</b> in order to monitor
the first ethernet device.
<p>A strongly worded warning in the README file encourages the user to follow
the recommended syntax:<br>
<pre>
NOTE: DO NOT PREPEND /DEV/ TO ANY OF THE DEVICES!!!
I MOCK ANYONE WHO ASKS ME HOW TO FIX THEIR COMPUTER
WHEN THEY ARE DOING THIS!
PROPER: netled console lo
NOT: netled /dev/console /dev/loop0
</pre>
<p>I'm curious as to the nature of the dire consequences implied by this
warning, but not curious enough to try it!
<p>NetLED can be started manually (I've aliased <kbd>'netled console ppp0'</kbd>
to <kbd>'led'</kbd>) or it could be started in either an init script or as an
addition to a PPP start-up script.
<p>If you would like to try it out, the source code can be obtained from this
WWW <a href="http://mars.ark.com/~mbevan/netled/">site</a>:
<p>http://mars.ark.com/~mbevan/netled/.
<hr>
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Last modified: Sat May 1 12:15:07 CDT 1999
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<center><H5>Copyright © 1999, Larry Ayers <BR>
Published in Issue 41 of <i>Linux Gazette</i>, May 1999</H5></center>
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