sysops cloud_computing, system_administration, owncloud

Evernote has been recently hacked. Dropbox has been hacked many times. Who knows what’s going in the other services we are using. So I decided to phase out my cloud service providers and create my own cloud. There are bunch of ways of running this tool. For instance, you can just download a VM image with everything installed. I decided to start from scratch and perform a manual installation on a new Ubuntu server. It’s very easy. First we need to install dependencies:

apt-get install apache2 php5 php5-gd php-xml-parser php5-intl
apt-get install php5-sqlite php5-mysql smbclient curl libcurl3 php5-curl

Then extract the downladed compressed file:

tar -xjf path/to/downloaded/owncloud-x.x.x.tar.bz2
cp -r owncloud /path/to/your/webserver

Set the directory permissions:

chown -R www-data:www-data /path/to/your/owncloud/

Enable .htaccess by settings AllowOverride to “All” in /var/www directory in Apache config which is in /etc/apache2/sites-enabled/000-default on Ubuntu Finally run mod_rewrite:

a2enmod rewrite
a2enmod headers

I got these instructions from Admin Manual which can be found here: ownCloud Admin Manual It’s quite straighforward. Then all we have to do is navigate to login page, create an admin account and start uploading files:

Own Cloud

My favourite features are:

  • Ability to share password protected links with specific users
  • Ability to set expiry date to shared files
  • Ability to sync mulitple local folders (it doesn’t have to mimic the directory structure of server, you can select and map separate folders)
  • Supports plugins. A simple note taking plugin is quite helpful to take and sync notes. Also I installed YubiAuth plugin which supposedly enables using my Yubikey with it. But couldn’t make it work yet. My only negative observation about it is SMTP settings didn’t work. When I tried to send someone a link of shared file I got a bizarre error. On their forums I saw other people having similar problems. To me it’s not a crucial issue (as a single user, who am I going to mail anyway) but for an organization it may quickly become an annoying issue.

devhobby neurosky, mindwave

To me a technology that enables you to collect data about your brain activity sounds fascinating. It always felt like Sci-Fi and unreachable. So when I heard about the affordable MindWave I immediately ordered it.

MindWave Mobile

This gizmo is manufactured by a company called NeuroSky focusing on brainwave technologies. I bought the MindWave mobile version as it has support to mobile devices which increases the possibilities of creating something cool. The best thing about it is that it comes with an SDK and you can develop your own applications on the platform. To get more info about the SDK visit They even have an app store that you can sell your applications. But the developer program costs $1500 so I don’t think I will sign up for that quite a while.

How does it work

The gadget communicates via Bluetooth. It supports lots of platforms and comes with an API ported to different languages. I prefered .NET and it worked without any problems. The real power of the device comes from the ThinkGear chipset. The API lets the developer to get results from the ThinkGear chipset. When you install the software bundled with the device, it installs ThinkGear connector and a bunch of games. First thing to do is pair the headset with your PC or iOS/Android device. Frankly, I didn’t quite like the applications that come with it. But it is not that important. After all I bought this thing to write my own programs against it.


The tutorial application, on the other hand, is very useful for testing the device and connection status.

Developing with MindWave

The starting point is definitely here:

The site steers the user very well so that you can select your goals and start developing right away. Actually the API is quite easy to use. After you connect you start receiving values from the sensor. In .NET wrapper the values are encapsulated in a class called ThinkGearState, which looks like this (I got this from its metadata):

public class ThinkGearState
    public float Alpha1;
    public float Alpha2;
    public float Attention;
    public float Battery;
    public float Beta1;
    public float Beta2;
    public float BlinkStrength;
    public float Delta;
    public bool Error;
    public float Gamma1;
    public float Gamma2;
    public float Meditation;
    public int PacketsRead;
    public float PoorSignal;
    public float Raw;
    public float Theta;
    public int Version;

    public ThinkGearState();

    public override string ToString();

The key fields for me are Attention and Meditation. BlinkStrength is also interesting. If you blink intentionally and strongly, the value wanders around 150 – 200. For normal blinks that we do quite often, it is around 50 – 60. So it is easy to differentiate if someone blinks. I wondered if this could be used as a communication method for Hector Salamanca in Breaking Bad. Instead of ringing a bell he could just blink. Admittedly it wouldn’t provide any extra functionality but it would look much cooler.

Breaking Bad Hector Salamanca

I don’t know how the Attention and Meditation values are calculated. The device also returns values for the various brain waves such as alpha, beta, theta, gamma and delta. I had no clue what these meant so here’s what I’ve learned from here and here.

  • Alpha: Increases in the state of physical and mental relaxation
  • Beta: Increases when we are consciously alert, or we feel agitated, tense, afraid
  • Theta: Shows the state of reduced consciousness
  • Delta: Increases when there is unconsciousness, deep sleep or catalepsy
  • Gamma: These waves are associated with peak concentration and extremely high levels of cognitive functioning

I don’t know why Alpha, Beta and Gamma waves return 2 values whereas Delta and Theta have only 1. As my knowledge on this subject is almost zero, I’ll just concentrate on the already-calculated Attention and Meditation values. I’ll try to develop a project using this gizmo and post it when it’ is ready. I think it is a very cool thing to have the ability to measure brain waves and write programs using those values. I guess the only problem for me is that I already constantly wear a wireless headset so it’s a bit hard to have them both on my head!


dev growl, raspberry_pi

I was going to write myself a desktop notification user control. I was planning it to be a simple window popping up when an event occurred. Before investing time and effort into this, I decided to look around to find a similar project and build on it. Unfortunately I couldn’t find something to my liking but discovered Growl. It has all feature you might expect from desktop notification tool. One additional feature that pleasingly surprised me is that you can send notifications to another machine over the network. This sounds good to me as I’m working on running my applications on Raspberry Pi using Mono lately. So the idea is to run the program on my Pi and receive the notifications on my desktop where I spend most of my time. Another benefit of Growl is that it is open-source which can be found here:

I don’t like my programs to be dependent on some external software that needs to be installed on the client machine but I thought this could be optional because desktop notifications can be one channel for communications and others can be added if necessary. So it is not a dependency but rather it enhancement in functionality. Also a pitfall in software development is the anti-pattern described as Not Invented Here. One simply cannot develop every piece of software needed to build complex systems. It’s not feasible. Of course when I write code on my own, my main goal is to learn something new but still I like to get results and produce working software. So best practices for commercial software still apply. Having convinced myself to use Growl for messaging I started looking for ways integrate it with my application. It comes with .NET SDK which is quite easy to use.

There are two assemblies need to be referred to:

  • Growl.CoreLibrary.dll
  • Growl.Connector.dll

The interesting bits are in Growl.Connector library. First you need to create an instance of GrowlConnectorclass. You can specify the remote hostname and password to send the notifications over the network which is what I wanted to do.

this.growl = new GrowlConnector("password", "", GrowlConnector.TCP_PORT);

Next, you have to register the application. If it is not registered, Growl will discard notifications coming from this source

this.application = new Growl.Connector.Application("Test notifier from ROHAN");
this.notificationType = new NotificationType(sampleNotificationType, "Sample Notification");
this.growl.Register(this.application, new NotificationType[] { notificationType });

Final step is to enable notifications over the network. By default it only accepts messages from the local machine.

Growl Security Settings

After the setup is completed we can send a test notification by this piece of simple code:

string text = string.Format("DateTime: {0}", DateTime.Now.ToString("dd/MM/yyyy HH:mm"));
Notification notification = new Notification(this.application.Name, this.notificationType.Name, DateTime.Now.Ticks.ToString(), "Mmessage from ROHAN", text);

And the result is:

Growl Message

So far so good. With only a few lines of code we managed to send a desktop notification over the network. We could specify a callback method to handle responses from the Growl host. We could also specify the encryption algorithm to enhance security. Now the last thing to test for me is to see it running on Raspberry Pi. To do that I created a sample console application that looks like this:

using System;
using Growl.Connector;

namespace MonoWorkout
	class MainClass
		public static void Main(string[] args)
			GrowlConnector growl = new GrowlConnector("password", "", GrowlConnector.TCP_PORT);
			growl.EncryptionAlgorithm = Cryptography.SymmetricAlgorithmType.PlainText;
			Growl.Connector.Application application = new Application("Test notifier from Raspberry Pi");
			NotificationType notificationType = new NotificationType("SAMPLE_NOTIFICATION", "Sample Notification");
			growl.Register(application, new NotificationType[] { notificationType });

			Console.WriteLine("Type message to generate notification");

			string message = string.Empty;
			while ((message = Console.ReadLine()) != null)
				if (message == "q")
					Console.WriteLine("Quitting program");

				string text = string.Format("DateTime: {0} \t Message: {1}", DateTime.Now.ToString("dd/MM/yyyy HH:mm"), message);
				Notification notification = new Notification(application.Name, notificationType.Name, DateTime.Now.Ticks.ToString(), "Message from Raspberry Pi", text);
				Console.WriteLine("Notification sent");

I ran the application but did not receive the results. I immediately ran WireShark and could see the packages coming to my desktop machine so it is not a network or firewall issue. After Googling a little bit I’ve found that there is Mono branch in the source code. I downloaded it and replaced the binaries with their Mono counterparts. Tested it again but to no avail.


When I sent the message I can clearly see it in wireshark but I don’t know why Growl is rejecting them. I ran the same application in both a Windows 7 instance and Raspberry Pi and captured the message packets. Outcome is interesting:

Here’s the message sent from Windows:

GNTP/1.0 NOTIFY NONE MD5:C5FB01D47A56832A17B3F941BC6F327F.3ECBA79D164DA5F8
Application-Name: Test notifier from Raspberry Pi
Notification-ID: 634982701932496447
Notification-Title: Message from Raspberry Pi
Notification-Text: DateTime: 07/03/2013 16:23 	 Message: TEST_ROHAN
Notification-Sticky: No
Notification-Priority: 0
Origin-Machine-Name: ROHAN
Origin-Software-Name: GrowlConnector
Origin-Platform-Name: Microsoft Windows NT 6.1.7601 Service Pack 1
Origin-Platform-Version: 6.1.7601.65536
And this is the one coming from Raspberry Pi:
<pre name="code" class="c-sharp:nocontrols">
Application-Name: Test notifier from Raspberry Pi
Notification-ID: 634982703645630380
Notification-Title: Message from Raspberry Pi
Notification-Text: DateTime: 07/03/2013 16:26 	 Message: TEST_RASPBERRYPI
Notification-Sticky: No
Notification-Priority: 0
Origin-Machine-Name: raspberrypi
Origin-Software-Name: GrowlConnector
Origin-Platform-Name: Unix

There is a 16 byte block at the beginning and I believe because of that Growl cannot parse the message therefore end up discarding it.

At this point, I’ll shelf this problem and look for alternative solutions. I hate leaving a problem unsolved like this but it is not a crucial feature so I’d rather not invest too much time into it. So for now my official opinion is, despite the Mono branch in the SVN, I don’t think Growl supports Mono.