Dynamic IP: remote notification of changes

Forum: Networking
Topic: Dynamic IP: remote notification of changes
started by: gjhicks

Posted by gjhicks on Mar. 03 2006,12:42

Hi,

Like many other ADSL users, I do not have a static IP, with my ISP changing my IP address at a irregular intervals.

Using 'ssh' with a redirected port and WinSCP, I can access my DSL server remotely. One problem - how to know the current IP address of the DSL server?

Below is my solution:

1) Install 'cron' (use apt-get)

2) Use cron to call the following script (I am sure the script could be more elegant but I am just a beginner):

#!/bin/bash
#
# Get the current external IP address of the DSL server,
# via the 'whatismyip' webpage

wget -q < http://www.whatismyip.com/ >

# Get just the first line, that is the string containing the IP address,
# then trim from the left to remove the html formatting

grep '<title>WhatIsMyIP' index.html | \
awk '{ d = length($3); print substr($3, 1, d-8) }' > tmp1

# Get the current DSL server time and construct the output string

STR1=$(date)" - DSL Server: Current IP Address = "$(cat tmp1)

# Write the string to a file

echo $STR1 >myip.txt

# Use the command line ftp to send the file to a server,
# using .netrc to automate the process

ftp ftp.servername.com

# clean up
rm index.html
rm tmp1

3) Contents of /home/dsl/.netrc

machine ftp.servername.com
login ftp-username
password mypassword
macdef init
prompt
hash
lcd /home/dsl
cd public_html
mdelete myip.txt
put myip.txt
quit
# newline terminates macro

4) Crontab contents

0 2,6,10,14,18,22 * * * /home/dsl/myip.sh

The above instruction runs the myip.sh script every 4 hours from 2am.

By the way, to create or edit the crontab instruction file, you need to set up the editor used by crontab, which defaults to /usr/bin/editor. I made a symbolic link to /bin/nano.

The end result is that, entering the URL to the text file in a browser, I get the current IP address for the DSL server.

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BUT, I would much rather email the text file but I can not get a command line email agent to work in DSL.

Can anyone help me figure out how to get a command line email agent working in DSL?

Thanks

Geoff.