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GnuDIP Release 2.3.5 - Windows Client Script
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<img align=middle src="gnudip.jpg" alt="GnuDIP Logo" border=0 height=60 width=113>
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<h1>GnuDIP Release 2.3.5 - Windows Client Script</h1>
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<hr>

<p>
With this client you can have your IP address updated automatically at
several GnuDIP sites simultaneously. This client will only send an update
to the GnuDIP servers if the IP address at the time of the last update
is no longer valid, or enough time has expired. The validity of the old
address is determined without generating any network traffic.

<p>
The <code>gdipc.bat</code> script serves as the GnuDIP client.
The <code>encpass.bat</code> is also described below. These scripts are simultaneously
Perl scripts and Windows <code>bat</code> files.

<p>
We assume from here on that you have installed
this Windows client in <u><code>C:\gdipc</code></u>.

<p>
We also assume that you chose to have <code>C:\gdipc</code> listed in your
<u><code>%PATH%</code></u> environment variable during the installation of this client
software. Thus you should be able to run <code>gdipc.bat</code> at the command prompt
like this:

<blockquote><pre>
C:\>gdipc -c
</pre></blockquote>

Otherwise at the command prompt you will have to use:

<blockquote><pre>
C:\>C:\gdipc\gdipc.bat -c
</pre></blockquote>

<p>
As a convenience, you may also run <code>gdipc -c</code> by simply opening
(e.g. <b>double-clicking</b>) the file <b><code>C:\gdipc\config.bat</code></b>. 

<p>
The client's features include:

<ul>
<li>
The client maintains the information for several GnuDIP domains in the same configuration
file. Using "<code>gdipc -c</code>" will replace any existing entry.
To list the entries or
delete an entry the user must use a text editor. There is one line per GnuDIP domain. 

<p>
The script <code>encpass.bat</code> takes its plain text password argument
and prints the encrypted version. This script faciliates manual modification of the configuration
file.

<p>
<li>
The format of the lines in the configuration file is demonstrated by this
sample configuration file:

<pre>
tester;gnudip;gateway;f5d1278e8109edd94e1e4197e04873b9;C:/GDIPC/gdipc.cache.tester.gnudip.txt;0;2073600
tester2;gnudip;gateway;f5d1278e8109edd94e1e4197e04873b9;C:/GDIPC/gdipc.cache.tester2.gnudip.txt;0;2073600
</pre>

<p>
<li>
The client tries not to abuse a GnuDIP server, and maintains a cache file for each GnuDIP
domain towards this end. This is reflected in the user interface, of which this is a sample:

<pre>
C:\>gdipc -c
Using Update Configuration Mode
Configuration file name: C:/GDIPC/gdipc.conf.txt
Username: tester
Domain: gnudip
Connect by direct TCP (d) or web server (w) [d]:
GnuDIP Server - host[:port]: gateway
Password: tester
Cache File [C:/GDIPC/gdipc.cache.tester.gnudip.txt]:
Minimum Seconds Between Updates [0]:
Maximum Seconds Between Updates [2073600]:
</pre>

This is a sample update run:

<pre>
C:\>gdipc
====  gdipc.pl running:  Mon Jun  4 17:59:19 2001  ====
Configuration file name: C:/GDIPC/gdipc.conf.txt
Cache file name: C:/GDIPC/gdipc.cache.tester.gnudip.txt
No update done for tester.gnudip - 192.168.0.4 still valid
Cache file name: C:/GDIPC/gdipc.cache.tester2.gnudip.txt
Invalid login attempt for tester2.gnudip
</pre>

The IP address for <code>tester.gnudip</code> was not updated because the IP address
at the time of the last update is still valid, and because
"Maximum Seconds Between Updates" had not yet expired.

<p>
This is the contents of <code>C:\GDIPC\gdipc.cache.tester.gnudip</code>:

<pre>
192.168.0.4;991699066
</pre>

The status of a GnuDIP domain may be reset by deleting its cache file.

<p>
If "Minimum Seconds Between Updates" is specified, then an update will not be sent to
the server more often than this interval, even if the IP address at the time of the last
update is no longer valid.

<p>
<li>
The "help" printed by the script is as follows:

<pre>
C:\>gdipc -h
usage: gdipc.bat \
usage:   { -h | -v | -i [ -r] | [ -f configfile ] [ -c | -r | \
usage:       [ -o outfile | -a appendfile | -l logfile ] \
usage:       [ -g sendport:recvport ] [ -d repeatseconds] \
usage:       [ -w waitseconds] [ -q "addressquerycommand" ] ] \
usage:       [ -x "addresschangedcommand" ] }
usage: With no arguments, update server if address changed or time
usage: expired.
usage: -h: Print this usage message.
usage: -v: Show version information.
usage: -i: Prompt and read standard input rather than a configuration
usage:     file.
usage: -f: Specify a particular configuration file.
usage:     This will otherwise be .GnuDIP2.txt in the directory
usage:     specified by the HOME environment variable, or gdipc.conf.txt
usage:     in the directory of the binary if HOME is not set.
usage: -c: Specify contents to write to configuration file.
usage: -r: Send an offline request to the server to remove your DNS hostname.
usage: -d: Run as a daemon. Perform client action immediately and then every
usage:     "repeatseconds" seconds.
usage: -o: Specify log file to overwrite on each run with output from script.
usage: -a: Specify log file to append on each run with all output from script.
usage: -l: Specify log file for daemon mode. Overwrite on first run, then
usage:     append.
usage: -w: Timeout in seconds when waiting for address validation packet.
usage:     Defaults to 1 second. Decimal point and fraction (e.g. "0.5") is
usage:     allowed.
usage: -g: Client is behind a gateway. Request GnuDIP server to register
usage:     address it sees connection from, and pass it back in response.
usage:     Specify port to send address validation packet to and port gateway
usage:     will forward it to.
usage: -q: Command to invoke to determine IP address to report to GnuDIP
usage:     server. Command must write address to standard output. When used
usage:     with -g, address is sent to server.
usage: -x: Command to invoke if address changed. This command can be used to
usage:     to take any actions required when the address changes. All
usage:     validated addresses are passed as arguments.
</pre>

<p><li>
If your internet connection is established at system start up (as for example with
DHCP), you will want to run <code>gdipc.bat</code> at system startup, using the
"Windows Task Scheduler" ("Scheduled Tasks" in "My Computer" - see
<a href="http://support.microsoft.com/support/kb/articles/q178/7/06.asp">
http://support.microsoft.com/support/kb/articles/q178/7/06.asp</a>).

<p>
On the author's version of Windows 98 this goes like this:

<p>
<ol>
<li>Double-click "My Computer", and then double-click "Scheduled Tasks".
<li>Double-click "Add Scheduled Task", and then click "Next". 
<li>Click "Browse".
<li>Locate and select the <code>gdipc.bat</code> file, as a temporary measure.
<li>Click "Open".
<li>Provide a name for the entry - perhaps "gdipc at start up".
<li>Select the "When my computer starts" radio box.
<li>Click "Next".
<li>Select the "Open advanced properties ..." option box.
<li>Click "Finish".
<li>Type the real command line (see below) into the "Run" text box.
<li>Click "OK".
</ol>

<p>
According to the Microsoft Web site:

<blockquote>
NOTE: To use Task Scheduler, you must log on to the computer with a valid user account.
</blockquote>


<p>
The command line for this could be:

<pre>
c:\gdipc\gdipc.bat
</pre>

This would open a console Window for its output, which would disappear after
<code>gdipc.bat</code> finished.

<p>
You could capture the output from the run by instead using:

<pre>
c:\gdipc\gdipc.bat -o c:\gdipc\gdipc_log.txt 
</pre>

<p>
The preceding command line would still open a console Window for its output,
which would disappear after
<code>gdipc.bat</code> finished. However, nothing would be displayed in the console window.
To eliminate the console window you could instead use:

<pre>
c:\gdipc\wperl.exe c:\gdipc\gdipc.bat -o c:\gdipc\gdipc_log.txt
</pre>

The difference here is the use of the <code>wperl.exe</code> executable instead of
the <code>perl.exe</code> executable. A console window is created by
<code>perl.exe</code> but not by <code>wperl.exe</code>.

<p><li>
If your IP address may change while your system is running, or you use manually
invoked dial up networking connections, you could have the
Windows Task Scheduler run this once a minute (or whatever), in addition to 
running it at system start up. Note however that the
<code>gdipc_log.txt</code> will be overwritten with each execution of
<code>gdipc.bat</code>. For this reason, you may want two separate Task Scheduler
entries - one for execution at start up and a second for the repeating executions.
For the repeating executions use:

<pre>
c:\gdipc\wperl.exe c:\gdipc\gdipc.bat -a c:\gdipc\gdipc_log.txt
</pre>

The difference here is the use of the "<code>-a</code>" option so that output is
appended to the log for each repeating execution. Note that you should also invoke
<code>gdipc.bat</code> with the <code>-o</code> option at system start up, or the
log file will grow indefinitely.

<p>
Again, on the author's version of Windows 98 the "Scheduled Tasks" part goes like this:

<p>
<ol>
<li>Double-click "My Computer", and then double-click "Scheduled Tasks".
<li>Double-click "Add Scheduled Task", and then click "Next". 
<li>Click "Browse".
<li>Locate and select the <code>gdipc.bat</code> file, as a temporary measure.
<li>Click "Open".
<li>Provide a name for the entry - perhaps "gdipc repeating".
<li>Select the "Daily" radio box.
<li>Click "Next".
<li>Click "Next" again.
<li>Select the "Open advanced properties ..." option box.
<li>Click "Finish".
<li>Type the real command line (see below) into the "Run" text box.
<li>Select the "Schedule" tab.
<li>Click the "Advanced" button.
<li>Select the "Repeat task" option box.
<li>Use the "Every" scroll box and list box to set your interval.
<li>Click "OK".
<li>Click "OK" again.
</ol>

<p>
If your IP address is particularly
volotile, you should specify a value for "Minimum Seconds Between Updates" of
1800 (30 minutes) or so, to give the GnuDIP server a break.

<p><li>
If you want to have the address validation done more often than once per minute,
and are willing to leave the GnuDIP client running continually, you could instead
schedule the client at system startup using a command line like this:

<pre>
c:\gdipc\wperl.exe c:\gdipc\gdipc.bat -d 30 -l c:\gdipc\gdipc_log.txt
</pre>

<p><li>
If you have an internal network with a <b>Network Address Transalation/IP Masquerading
gateway</b> providing access to and from the public Internet, and you want to register
the external IP address of the NAT box with the GnuDIP server, you may want to run the
client on an internal machine. If the gateway is a closed proprietary device, you will
have to run the client on an internal machine. 

<p>
The client normally sends the address it detects at its end of the connection to
the server in the update request to the server, and the server registers this
address. It also remembers this address, and tests whether it is valid by sending
a UDP packet to a randomly selected port at this address. The client then waits
a short interval to receive this packet. If it is not received the IP address
is assumed to have changed, and an update is sent to the GnuDIP server.

<p>
To run behind an NAT box, the client needs to know the external address of the NAT box
and must be able to check whether that address has changed.

<p>
You must configure the NAT box to redirect some external UDP port to a UDP port on
the internal machine running the client. You provide these port numbers to the
client using the <code>-g</code> option. This option will
also cause the client to request the GnuDIP server to send the external
address of the NAT device (which the server sees as the other end of the client connection)
back in the reply to the update request. You must ensure that the GnuDIP servers you use
are at release 2.3.2 or later in order for this request to succeed.

</ul>

<p><hr>

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