Friday, December 27, 2013

The pi-web-agent

Remember the Hackmanchester winning project pi-web-agent? Well, we released the first version of the pi-web-agent in the pistore. Here is the wiki page of the project as generated and exported from our github repository


The pi-web-agent is a web application that aims to provide a more user friendly way of interacting with the Raspberry Pi and performing basic tasks by eliminating the need of using the command line directly.

How to use

After starting the pi-web-agent service by executing or sudo /etc/init.d/pi-web-agent start , you can access the application with your browser via either https://raspberrypi:8003 or https://ip_address_of_your_pi:8003 if your internet router does not resolve hostnames to IPs. To access the application inside your Pi just access the local host without https:

Provided functionalities

The web application currently provides the following functionalities:

  • Firewall management by controlling the iptables.
  • A package management system for installing useful applications easily.
  • Service management for starting or stopping services
  • Update management for updating the underlying Linux distribution with a simple click
  • GPIO management for controlling the pins on the Raspberry Pi (special thanks to the author of wiringPi for his excellent open source program)
  • General purpose information of the system (memory usage, disk capacity, ip, cronjobs, swap usage)
  • Tightvnc is provided, by setting up a vncboot service and enabling users to use tightvnc java applet to access the system by the tightvnc viewer (special thanks to tightvnc for their open source tightvnc client)
  • Power management for rebooting or powering off the system with a simple click

Firewall management

Currently the Firewall management section displays the current state of the iptables. Enabling input for altering the iptables state is under development

Package management

The package management provides a list with useful packages and a short description. You can request an uninstall or install of the application by simply clicking on the switch button.

Service management

Service management allows you to stop or start services. Only services with known state are shown.

Update management

The update management aims to arrange or the hassle about updates for you. It takes care of checking for updates and notifies you on the live information feed. The update section also provides information of weather there is an update or not and if yes, it provides a list of packages with there description that need update. The update can be initiated with a simple click of a button at the end of that list.

GPIO management

The GPIO management provides access to the General Purpose Input Output pins on the Raspberry Pi. You can convert a pin to input or output and activate outputs. Currently only GPIO0-GPIO7 pins are available. The solution is under development to provide more functionality on the second release.


VNC is very important because most users want to access their pi from their laptop and have an image of the desktop in their screen. That's why the application has the tightvnc server as a dependency and provides the tightvnc client java applet. The whole vnc solution is pre-setup and only clicking at the vnc section should work. The tightvnc service on the RPi should be started manually because you need to setup a password.


Currently the web application agent supports the Raspberry Pi with Raspbian installed. Any debian based Linux distribution should also work but is not thoroughly tested yet.


Vasilis Nicolaou, Angelos Georgiadis, Georgios Chairepetis, Kyriacos Georgiou and Maria Charalambous


GPLv2. Imported projects have their own license.

Developer information

Please consult the README file in order to setup an environment for testing purposes of the application. Note that architecture specific code won't work (just the GPIO for the moment). The application is based on the micro-CernVM web appliance agent developed at CERN by Vasilis Nicolaou and documentation section contains documents for that web application but are highly relevant to the forked version (the pi-web-agent)


Report (only relevant information of the web application, ignore update management section)

Presentation (first 9 slides)

Follow usr/share/pi-web-agent/doc for documentation on key python modules.

Thursday, January 31, 2013

A Dropbox client for the raspberryPI


Raspybox is a minimalistic but powerful dropbox client written in python for the RaspberryPI.

How to use it

There are three forms that the program can be executed. The simplest is the graphical way. First you have to execute and type login. Follow the instructions and when you finish press ctrl+D to exit. Now you can use it in any of the three forms.

Setting things up

You need to install the dropbox sdk for python (which can be found in dropbox developer page) and create your own app. Download all the files from the file directory of this project and place them in a directory. Create an app for the whole dropbox and copy paste the keys in accordingly.

User Interfece

To execute the user interface simply type ./ . The user interface should come up after a few seconds.
You can also use some shortcuts instead of the menu:
For upload press insert key.
For delete press delete key.
To refresh press F5
To navigate through your directories use the arrow keys and enter or double mouse click to either enter a directory or download a file.
There will be some messages in the console, don't worry about them. If the program crashes send the output as a bug report to the developer. This is because it is the initial version, so it might have some serious bugs.

Dropbox command line

You can also execute the and use the dropbox from the command line. Type help to view the necessary commands.

Alternative command line

Because the RaspberryPI is very useful when using scripts and command line fire and forget programs such a functionality is supported. Instead of running ./ to access command line, you can supply a dropbox command as argument. Then the program will start-up execute the command, display the output and die. Be ware that the cache can't work on such situations. You can modify it to keep a cache on a file instead of the memory or use your own in your script.
This part however needs further development and consideration, so the command line can be used efficiently and fast enough (for example it makes no sense to run a command for changing directory, it will be of no use for this purpose)


Currently the code is not very well commented, but it should not be very difficult to understand it, since it's a small program. However, a commenting will be done soon, I hope. If you want to contribute to this program, please send a request.

Currently, the target groups are developers, testers and PI hobbyists, but anyone can have a go with it.
You can find everything here:

Wednesday, January 2, 2013

Finding probabilities for RISK

During holidays we find ourselves playing board games. One of the best out there is RISK. During game-play, one might wonder what are the probabilities for each battle scenario. Moreover, if that someone is, well, a geek, he might write a program during game-play to support his army with a little of, em, technology.
So, do we know an equation to find those probabilities? No. Probably we'll find one with a little google search, but why not study it using a more programming method? We have the technology, we know a little bit of programming, so, let's take our chances.

  1. import java.util.Arrays;
  2. public class RiskProbability
  3. {
  4. private static int[] diceThrow(int n)
  5. {
  6. int[] dice = new int[n];
  7. for (int i = 0; i < dice.length; i++)
  8. dice[i] = (int)(Math.random()*6) + 1;
  9. Arrays.sort(dice);
  10. return dice;
  11. }
  12. public enum winner {ATTACKER, DEFENDER, TIE};
  13. private static winner battle(int a, int d)
  14. {
  15. int[] attacker = diceThrow(a);
  16. int[] defender = diceThrow(d);
  17. int aSoldiersLost=0;
  18. int dSoldiersLost=0; 
  19. int j=defender.length - 1;
  20. for (int i = attacker.length - 1; i >= 0 && j >= 0 ; i--)
  21. {
  22. if (attacker[i] > defender[j--])
  23. dSoldiersLost++;
  24. else
  25. aSoldiersLost++;
  26. }
  27. if (aSoldiersLost > dSoldiersLost)
  28. return winner.DEFENDER;
  29. else if (dSoldiersLost > aSoldiersLost)
  30. return winner.ATTACKER;
  31. else
  32. return winner.TIE;
  33. public static void main(String[] args)
  34. {
  35. int experimentSize = Integer.parseInt(args[0]);
  36. int attWins = 0, defWins = 0, ties = 0;
  37. int attStyle = Integer.parseInt(args[1]);
  38. int defStyle = Integer.parseInt(args[2]);
  39. for (int ex = 1; ex <= experimentSize; ex++)
  40. {
  41. winner w = battle(attStyle, defStyle);
  42. switch (w)
  43. {
  44. case ATTACKER: attWins++; break;
  45. case DEFENDER: defWins++; break;
  46. case TIE: ties++; break;
  47. defaultbreak;
  48. }//switch
  49. }
  50. System.out.println("Experiment is with " + attStyle + " attackers and " + defStyle + " 
  51. defenders " + experimentSize + " times");
  52. System.out.println((attWins/(double)experimentSize) + " attackers");
  53. System.out.println((defWins/(double)experimentSize) + " defenders");
  54. System.out.println((ties/(double)experimentSize) + " ties");
  55. }//main
  56. }
Let's explain the code a bit.
Lines 4-11 is the definition of a throw dice function. You specify the number of dice to throw, and a sorted array of the values of each die is returned. Watch out because the dice are sorted in ascending order.

Line 12 is an enumeration to be used for specifying the winner.
Line 13 is the definition of the battle function that takes two arguments, the number of dice the attacker will use and those of the defender as a second argument. Then the diceThrow is called and the battle begins on lines 20-26 until one runs out of dice.
Line 34 is the main method where the battle is initiated for 'experimentSize' number of times using the specified number of dice for each player.
To run this properly you have to pass 3 integer arguments, the experiment size (1000000 should be more than enough), the number of dice of the attacker and the number of dice of the defender. These are the results obtained by using the above program:

$ java RiskProbability 1000000 3 2
Experiment is with 3 attackers and 2 defenders 1000000 times
0.371734 attackers
0.291923 defenders
0.336343 ties

java RiskProbability 1000000 2 2
Experiment is with 2 attackers and 2 defenders 1000000 times
0.227412 attackers
0.448301 defenders
0.324287 ties

$ java RiskProbability 1000000 3 1
Experiment is with 3 attackers and 1 defenders 1000000 times
0.66038 attackers
0.33962 defenders
0.0 ties

$ java RiskProbability 1000000 2 1
Experiment is with 2 attackers and 1 defenders 1000000 times
0.578971 attackers
0.421029 defenders
0.0 ties

$ java RiskProbability 1000000 1 1
Experiment is with 1 attackers and 1 defenders 1000000 times
0.416221 attackers
0.583779 defenders
0.0 ties

$ java RiskProbability 1000000 1 2
Experiment is with 1 attackers and 2 defenders 1000000 times
0.25389 attackers
0.74611 defenders
0.0 ties

So, the next time you'll play RISK, you'll know.