One important thing in programming today is XML. Many applications rely on XML because it want to store hierarchical data in persistent storage aka file. This truth is applied to most Java application because it seems, in my opinion, Java has the most larger sets of XML libraries from the top to the ground. In other words, ones may do anything with XML in Java very easy. Unfortunately, I am not a good Java programmer in any point of view. My favorite language is Python and OS is Linux. XML in Python is not as good as that one in Java. That's a problem.

RSA is one of the most well-known security infrastructure based on PKI. I'm talking about how to generate a key-pair to be used in applications.

Since I switched my laptop to Ubuntu for a few months, it is necessary to build some packages myself to get the most up-to-date features or to install custom program properly. My background is all RedHat-based distribution and its RPM. I'm learning DEB.

One of the most web application server in open source community is Apache Tomcat. The latest stable version is 5.5.20. It is possible to develop a web application that tightly interfaces to SAP R/3 or its components via SAP JCo aka SAP Java Connector. Its latest version is 2.1.7. It is a little bit tricky to run SAP JCo inside Apache Tomcat on Linux.

It has been a while since Gaim 2.0.0 beta 5 came out. It works so great! Only one thing I really hate is the blank filename on file transfer. It is very annoying me everytime I got files from my friends. Fortunately, it was closed last week. It's the good news. The bad one is that this patch seems to be appeared in beta 6 and there is no tentative timeframe yet. However, the power of opensource is I don't have to wait. Everything I want, I might do it myself. Anyway, I don't have enough time to figure out where the problem is so I have to wait for the patch. Now, the patch is available. I may wait for beta 6 or compile it myself to make it work early. I have enough time to compile for sure!

Sometimes, the standard kernel bundled with Ubuntu may not fit your environment. For example, your server is attacked regularly via bad behavior in the network. This behavior is called denial-of-service or DoS. There are so many techniques to DoS someone. The most classic one is TCP SYN flood. The effect of this attack is to full the backlog buffer in kernel. Anyway, this attack is not popular anymore. Recent kernel could handle this attack easily because it is very easy to detect TCP SYN flood. However, the worst thing I don't want to see is the attacker flood the server by established TCP connection. It is hardly to distinguish this attack from normal behavior. There are several workaround to protect the server against this attack.

1. Decrease socket timeout
2. Limit the number of concurrent connection per IP address