Showing posts from 2006

Hole Punching: To Do Or Not To Do

Hole punching technique is nothing new. It is as old as the firewalls through which it punches hole. But due to the huge popularity of Skype which does hole punching to make VoIP work even when behind firewalls and due to the apparent inability of network administrators to block them, there is a new wave of articles on this topic.

Slashdotcovered one such article. After reading the comments there it became clear that many don't really understand how protocols like TCP and UDP work or why hole punching works.

Hole punching head-ache at office:
Hype is that network administrators will have a lot of headache managing the bandwidth consumed by all these p2p applications that punch holes and "illegally" transfer data. But that isn't the case in reality. Network administrators have a variety of options at their disposal. Like in case of Skype, they can always block the various Skype central site IP addresses. Also, an advanced stateful firewall like IPTables in Linux can be c…

Free Google for Small Businesses!

Most people think Google is a search company! Well, yes they are a search company. But primarily they are a very good web technology company. What they do brings Internet and its way of life much closer and more easier to many people. Can you imagine that if you are a small business owner, you have quite a few things going for you because of Google. The product of theirs I'm referring to here is Google Apps for Domains.
Google Apps for Domain provides free e-mail (2GB) accounts at your domain address. This, along with the google talk messenger service at the same address, pages, and calendar make it a pretty nice offering, all for free. Also, throw in a restricted private groups at google groups beta, you have a pretty good online infra structure for your company! Very reliable, secure and free!

I just setup all this for a company called SSC Vanilla. And the handful of people at this company are already using it and seeing the benefits.

More to come later, may be.

Google 403 Bot Error! on trying to set preferences from Firefox!

Today I searched for "form $PHP_SELF" on Google the search within Firefox. I got 10 results. I wanted more. So, I hit preferences and changed the number to 100. When I save the preferences and it gets back to the page, this is what it says!

We're sorry...... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now. We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected, you might want to run a virus checker or spyware remover to make sure that your systems are free of viruses and other spurious software. We apologize for the inconvenience, and hope we'll see you again on Google.

Then I opened google home page, went straight to preferences and changed results to 100 and then did my search. viola! everything was fine! So there was nothing inherently wrong wi…

Microsoft Office 2007 First Impressions!

I just got my hands on Microsoft Office 2007. My first impression about it is very positive. Its very slick and nice. The UI is very refreshing and easy to use. And its faster and intelligent. I've tried just the Word, Excel and Powerpoint till now. Saving Powerpoint to pdf is very nice. It needs a plugin to be installed. Its not obvious why they didn't include it by default.

Although the installation took a lot of time, it was very easy and asked few questions. It detected and upgraded my Office 2003 installation.

Outlook 2007 still sucks. Nothing much different. Too slow and still hangs with IMAP over SSL.

Probably I post a more detailed review later.

Once again, Microsoft has made sure that its stronghold office presence isn't threatened by any other Free or commerical offerings.

Access Apache WebDAV from Windows XP

This is a work-in-progress. This is not complete, may be never will be. It is purely for my own reference. Use at your own risk.

Here I try to remember how to configure Apache and Windows XP so that WebDAV on Apache
is accessible from Windows XP clients.


Registry changes required to support large files and many files:

Automatic Protocol Driver Selection for MSDAIPP

DHTML Behaviors for making webfolder open automatically.… - Google - Yahoo - Microsoft!

Seems like the search engine #1 #2 and #3 have come together to cook up something to make their jobs easier. Meet Basically you tell them the links your site using a xml file and let them know what you think is relatively important. There was already a "Sitemaps" as part of Google Webmaster's Tools which had similar features. Its good that they standardized the protocol across three major search engines and have made the specification licensed under Attribution-ShareAlikeCreative Commons license. And there are many online sitemaps generators. But there seems to be no way to add one to blogspot.

Apache Notes

My Apache configuration:
./configure --enable-pie --with-mpm=worker --enable-exception-hook --enable-auth-digest --enable-deflate --enable-expires --enable-suexec --enable-rewrite --enable-so
make install

This installs everything in /usr/local/Apache2/

cgid daemon runs as the user configured in apache configuration and shuts down fine.

Work Items:
Optimizations. For Speed and Size.
Security: Suexec modifications.
Directory Layout changes. --with-layout.

Code Commentary: dvd-audio tools

Recently I've got interested in dvd-audio free software. I'm getting a universal player. So then want to be able author my own content in high definition multi-track audio DVD. Currently there is only one DVD Audio authoring free software hosted at

This project hasn't been worked on since its last alpha release on 20050703. And there are some nice TODO items on its status page. Some of them are really good to have. So I'm thinking of working on them.

To start off, I would comment on the code and log it here for my understanding and reference. (might help others too!).

Source I'm using for this purpose is taken from here.

Let's look at the source code organization.
amg.c /amg.h - has code for Audio Manager (AMG) - this is stored in the AUDIO_TS.* files and consists of the AUDIO_TS.IFO file, an optional moving video menu in the AUDIO_TS.VOB file and the backup file AUDIO_TS.BUP.

samg.c /samg.h - has code for Simple Audio Manager (SAMG…

Writing Apache 2.x Filters

I'm writing a Apache 2.x output filter to append arbitrary query parameter variables to all the urls in the response body. Some of the references online that helped me get started on the output filter are listed below. For the actual work of finding the url tags, extracting the url and appending the required query param, I'm using a Lex scanner. (no parser required).

Flex Resources:
GNUwin32 package of flex. (Oh! btw, I started off on windows. 'cuz we need it both on Windows nd Linux and I know it will surely work in Linux as I've used flex/bison in Linux before.) & yacc, Second Edition
Apache Reference Online:

This is the website. Most of the pages are in German; but you can make out.
The specific presentation I was talking about are here:

Then, there is…