Category Archives: programming

How to use XMPP SASL EXTERNAL with Node.js

Almost a year ago I came across Node.js for the first time. Without going into details I must admit that a kind of like it. It has been useful to me in various projects. I especially like it for rapid … Continue reading

Posted in programming | Tagged , , , , , | Leave a comment

Google Maps icons and circles revisited

Recently I needed to add icons and circles to a Google Map. My colleague Jan Sipke did a nice write up on this topic a couple of years ago. Unfortunatly things did change since then. Google released a new version of the Maps API … Continue reading

Posted in programming | Tagged , | Leave a comment

Grep lines before and after matched line

The command grep is really useful for finding matches of a certain word in files or streams. However, until recently I didn’t know how to display lines before and after the matched line(s). Let’s say we have a file named … Continue reading

Posted in programming | Tagged | 1 Comment

Temperature graphs

In a previous article we looked at remote measurement of temperature and humidity. Now it is time to show the results of the temperature measurements. First a recap of the setup: Three remote temperature and humidity sensors are located in … Continue reading

Posted in programming | Tagged , | 1 Comment

Measuring temperature and humidity with a JeeNode

In a previous article we looked at the Arduino. Now we will look at an (almost) Arduino compatible clone, the JeeNode. It is a bit smaller and cheaper than the original version and operates at 3.3V instead of 5V. This … Continue reading

Posted in Hardware, programming | Tagged , , , | 1 Comment

Programming the Arduino ethernet shield

The Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It features an IDE that allows you to program the Arduino using a standard USB cable. Several shields exist that extend the functionality of the … Continue reading

Posted in Hardware, Networking, programming | Tagged | 2 Comments

Model View Controller (MVC) with JSP and JSTL

In this article we will create a small web application that uses the Model View Controller (MVC) pattern with Java Server Pages (JSP) and JSP Standard Template Library (JSTL). A container like Tomcat is needed to run this combination. Thanks … Continue reading

Posted in programming | Tagged , , , | 3 Comments

Changing CPU and memory settings on XenServer VMs

You can change the CPU and memory settings of XenServer virtual machines using the API. XenServer allows you to set the priority of the virtual machine CPU (called weight), set a limit on the amount of CPU the virtual machine … Continue reading

Posted in Cloud computing, programming | Tagged , | 7 Comments

Installing Sun JDK 6 on Ubuntu 10.04

The Sun JDK can be installed on Ubuntu by adding a repository and installing with apt-get. The following works with the latest versions of both at the time of writing: Sun JDK 6 update 20 Ubuntu 10.04 sudo add-apt-repository “deb … Continue reading

Posted in programming | Tagged | 8 Comments

Getting CPU, memory, disk and network metrics from XenServer

In a previous article we looked at getting CPU and memory metrics from XenServer. As noted in that article, as of version 5.5 of XenServer, the preferred way of getting virtual machine metrics is through HTTP calls to get RRD … Continue reading

Posted in Cloud computing, programming | Tagged , | 1 Comment