# GnuDIP Release 2.3.5 - Windows Client Script

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 This client will only send an update to the GnuDIP servers if the IP address at the time of the last update is no longer valid, or enough time has expired.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.

The `gdipc.bat` script serves as the GnuDIP client. The `encpass.bat` is also described below. These scripts are simultaneously Perl scripts and Windows `bat` files.

We assume from here on that you have installed ActivePerl in `C:\perl` and this Windows client in `C:\gdipc`.

We also assume that `C:\perl` is listed in your `%PATH%` environment variable. The installation file for ActivePerl should do this for you. You may have to restart Windows for this to take effect though (certainly for Windows 9x).

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

>     C:\>gdipc -c

Otherwise at the command prompt you will have to use:

>     C:\>perl C:\gdipc\gdipc.bat -c

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

The client's features include:

- The client maintains the information for several GnuDIP domains in the same configuration file. Using "`gdipc -c`" 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.

  The script `encpass.bat` takes its plain text password argument and prints the encrypted version. This script faciliates manual modification of the configuration file.

- The format of the lines in the configuration file is demonstrated by this sample configuration file:

      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

- 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:

      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]:

  This is a sample update run:

      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

  The IP address for `tester.gnudip` 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.

  This is the contents of `C:\GDIPC\gdipc.cache.tester.gnudip`:

      192.168.0.4;991699066

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

  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.

- The "help" printed by the script is as follows:

      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.

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

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

  1. Double-click "My Computer", and then double-click "Scheduled Tasks".
  2. Double-click "Add Scheduled Task", and then click "Next".
  3. Click "Browse".
  4. Locate and select the `gdipc.bat` file, as a temporary measure.
  5. Click "Open".
  6. Provide a name for the entry - perhaps "gdipc at start up".
  7. Select the "When my computer starts" radio box.
  8. Click "Next".
  9. Select the "Open advanced properties ..." option box.
  10. Click "Finish".
  11. Type the real command line (see below) into the "Run" text box.
  12. Click "OK".

  According to the Microsoft Web site:

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

  The command line for this could be:

      c:\gdipc\gdipc.bat

  This would open a console Window for its output, which would disappear after `gdipc.bat` finished.

  You could capture the output from the run by instead using:

      c:\gdipc\gdipc.bat -o c:\gdipc\gdipc_log.txt

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

      c:\perl\bin\wperl.exe c:\gdipc\gdipc.bat -o c:\gdipc\gdipc_log.txt

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

- 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 `gdipc_log.txt` will be overwritten with each execution of `gdipc.bat`. 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:

      c:\gdipc\wperl.exe c:\gdipc\gdipc.bat -a c:\gdipc\gdipc_log.txt

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

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

  1. Double-click "My Computer", and then double-click "Scheduled Tasks".
  2. Double-click "Add Scheduled Task", and then click "Next".
  3. Click "Browse".
  4. Locate and select the `gdipc.bat` file, as a temporary measure.
  5. Click "Open".
  6. Provide a name for the entry - perhaps "gdipc repeating".
  7. Select the "Daily" radio box.
  8. Click "Next".
  9. Click "Next" again.
  10. Select the "Open advanced properties ..." option box.
  11. Click "Finish".
  12. Type the real command line (see below) into the "Run" text box.
  13. Select the "Schedule" tab.
  14. Click the "Advanced" button.
  15. Select the "Repeat task" option box.
  16. Use the "Every" scroll box and list box to set your interval.
  17. Click "OK".
  18. Click "OK" again.

  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.

- 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:

      c:\perl\bin\wperl.exe c:\gdipc\gdipc.bat -d 30 -l c:\gdipc\gdipc_log.txt

- If you have an internal network with a Network Address Transalation/IP Masquerading gateway 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.

  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.

  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.

  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 `-g` 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.