elCuervo

Airplay Protocol

2012-01-05T00:00:00-02:00

I've spent a lot of time figuring out how to connect to my AppleTV and send it pictures, videos, music, etc... then i've realize that there is no documented protocol for it. Apple just mantains the interface for Cocoa and hides the undelying protocol

The research to make the airplay gem was slow, mainly because was only a proof of concept to communicate with the AppleTV from ruby.

General Info

One of the first things to know is that the Airplay Protocol uses a subset of HTTP to communicate, uses an upgraded connections PTTH and persistent connections to the resources.

Second generation AppleTV with iOS 5 will also broadcast Airtunes and Mirroring through the LAN.

Finding the server

The AppleTV will broadcast himself in the LAN using Bonjour). You can find yours browsing for '_airplay._tcp.'.

This will give you and Ip and a port, normally being :7000.

Photos

The resource for photos is "photo" there are only a few things that you can do here.

You cannot send the path of the image, you need to send it's content so if you wanted so send an image you could only:

      $ cat image.jpg

      content = File.read(image_path)

Request

      # PUT /photo
      # X-Apple-Transition: None
      # Connection: Keep-Alive
      #
      # ... raw img content ...
      #

Please note the "X-Apple-Transition" header, this header is not mandatory with it you can create transitions between the current image and another.

The ones i've found are:

None
SlideLeft
SlideRight
Dissolve

Two of them will give the chance so simulate the slide as when seeing in an iPhone.

Request flow

+-----------+
|  AppleTV  +----+
+-----------+    |
                 |
       +---------+-----+
       |  PUT /photo   |
       |               |
       |  img content  |
       +---------+-----+
                 |
+----------+     |
|  Client  +-----+
+----------+

Video

The resource for videos is divided according for some it features, so you'll have "play", "stop", "rate".

play

Note three things:

There is a content in the body of the request, those are the 'commands' that make magic
The connection must be kept alive for all the time of the video playback.
The Start-Position command as it's name suggest will set the start position to n seconds of start.

Request

      # POST /play
      # Connection: Keep-Alive
      #
      # Content-Location: http://something.com/video.mp4
      # Start-Position: 0
      #

stop

This will stop (and end) the current playback

Request

      # POST /stop
      # Connection: Keep-Alive
      #

rate

This was a tricky one, rate it's just to pausing and resuming playback of media.

To pause:

      # POST /rate?value=0
      # Connection: Keep-Alive
      #

To play:

      # POST /rate?value=1
      # Connection: Keep-Alive
      #

Request flow

+-----------+
|  AppleTV  +----+
+-----------+    |
                 |
       +---------+---------------------------------------------------+
       |  POST /play                                                 |
       |                                                             |
       |  Content-Location: http://somewhere.com/overtherainbow.mp4  |
       |  Start-Position: 5                                          |
       +---------+---------------------------------------------------+
                 |
+----------+     |
|  Client  +-----+
+----------+

PostGIS in osx and debian

2011-12-29T00:00:00-02:00

I'm working in some cool GIS stuff using some shapefiles so i've finished using postgis... well... that was the idea, but i had some issues trying to setup everything in my mac so after some research i've found a gist that saved my life and here it is with some minor modifications. Hopefully in a few days i'll upload a tele script for it.

All the fame and fortune belongs to this gist

OSX

      #0. Setup some stuff
      db_name='name'
      db_user='user'

      # As in Postgres 9.0.1 in brew initdb causes some malloc issues
      sudo sysctl -w kern.sysv.shmall=65536
      sudo sysctl -w kern.sysv.shmmax=16777216

      # To make the changes permanent instead of just the running kernel
      echo "kern.sysv.shmall=65536\nkern.sysv.shmmax=16777216" >> /etc/sysctl.conf

      #1. Install PostgreSQL postgis and postgres

      brew install postgis
      initdb /usr/local/var/postgres
      pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start

      #2. Create a template to be used on creating GIS-enabled databases

      createdb postgis_template
      createlang plpgsql postgis_template

      # Import Postgis Data
      psql -d postgis_template -f
      /usr/local/Cellar/postgis/1.5.3/share/postgis/postgis.sql
      psql -d postgis_template -f
      /usr/local/Cellar/postgis/1.5.3/share/postgis/spatial_ref_sys.sql

      # Test if works
      psql -d postgis_template -c "SELECT postgis_full_version();"

      #3. Set template permissions to gisgroup
      createuser -R -S -L -D -I gisgroup;

      psql -d postgis_template
      ALTER DATABASE postgis_template OWNER TO gisgroup;
      ALTER TABLE geometry_columns OWNER TO gisgroup;
      ALTER TABLE spatial_ref_sys OWNER TO gisgroup;
      CREATE SCHEMA gis_schema AUTHORIZATION gisgroup;
      \q

      #4. Adds an app to your application
      createuser -i -l -S -R -P -d $db_user

      echo "GRANT gisgroup TO $db_user;\q" | psql -d postgres

      #5. Create your app database
      createdb -T postgis_template -O $db_user $db_name;

Debian

      #0. Setup some stuff
      db_name='name'
      db_user='user'

      #1. Install PostgreSQL postgis and postgres

      sudo apt-get install postgresql postgresql-client postgresql-contrib
      sudo apt-get install postgresql-8.4-postgis

      #2. Create a template to be used on creating GIS-enabled databases

      sudo su postgres

      createdb postgis_template
      createlang plpgsql postgis_template

      #Import Postgis Data
      psql -d postgis_template -f
      /usr/share/postgresql/8.4/contrib/postgis-1.5/postgis.sql
      psql -d postgis_template -f
      /usr/share/postgresql/8.4/contrib/postgis-1.5/spatial_ref_sys.sql

      #Test if works
      psql -d postgis_template -c "SELECT postgis_full_version();"

      #3. Set template permissions to gisgroup
      createuser -R -S -L -D -I gisgroup;

      psql -d postgis_template
      ALTER DATABASE postgis_template OWNER TO gisgroup;
      ALTER TABLE geometry_columns OWNER TO gisgroup;
      ALTER TABLE spatial_ref_sys OWNER TO gisgroup;
      CREATE SCHEMA gis_schema AUTHORIZATION gisgroup;
      \q

      #4. Adds an app to your application
      createuser -i -l -S -R -P -d $db_user

      echo "GRANT gisgroup TO $db_user;\q" | psql -d postgres

      #5. Create your app database
      createdb -T postgis_template -O $db_user $db_name;

Easy websockets with Cuba

2011-12-23T00:00:00-02:00

I have the urge to find simple solutions to complex problems, in that mad quest i've found myself reading extremely long libraries that do things in complicated ways just to have more 'features'. Nowdays the web only wants to add realtime in any sentence and thanks to HTML5 and Websockets it's a pretty easy thing to do but... doing that with ruby gets overcomplicated.

Trying to find a simple solution i've researched a lot. I've found Cramp to work pretty well, but requiring activesupport it's against my religion :D.

After some googling and githubbing i've found websocket-rack which is a clean and simple solution for a problem that it's actually simple.

      require 'cuba'
      require 'rack/websocket'

      class Websockets < Rack::WebSocket::Application
        def on_open(env)
          send_data("Welcome")
        end

        def on_message(env, message)
          send_data(message.reverse)
        end
      end

      Cuba.define do
        on "ws" { run Websockets.new }

        on "" do
          res.write "The websockets are in /ws"
        end
      end

This is a silly example, but enough in most of the cases, in here you will have to choose a way to id the clients and send them some messages but that's the fun part.

Gerbil, TDD for the rest of us

2011-12-02T00:00:00-02:00

Gerbil is my attempt to use a really simple (for real) tdd framework in js, both browser and node.js. The main idea is to provide a simple way to test certain behaviours like assert, assertEqual, assertThrow, etc. Currently the API in really simple and will eventually include some cool features.

Most of the time the tests that we need to execute are not THAT complex, one of my side project is Lodis an implementation in javascript of the well known Redis Server.

For it i'm using LocalStorage as foundation to implement the Redis commands, for that i needed a way to test things in the browser. But all of it seemed so complex for a simple console.log.

So i started that, a REALLY SIMPLE testing suite to do that, assert to console.log. Eventually i've needed some other things so it grow enough to release it.

Install

You can see the project in Github

Using npm

$ npm install gerbil

Or in a browser

https://raw.github.com/elcuervo/gerbil/master/build/gerbil.pack.js

A simple example

scenario("This is my scenario", {
  "setup":  function() {
    // When scenario starts
    this.someThing = new Thing;
  },
  "before": function() {
    // Before every test
    this.someThing.magic_magic();
  },
  "after":  function() {
    // After every test
    this.someThing.clean();
  },
  "cleanup": function() {
    // When the scenario ends
    this.someThing = false;
  },

  "MagicClass should have a length": function(g){
    this.someThing.add(1);
    g.assertEqual(this.someThing.length, 1);
  },

  "MagicClass should be valid": function(g) {
    g.assert(this.someThing.valid);
  }
});

Example output

Console

As i said node.js is supported so the output will look like this:

Browser

On the other hand if you ran it within a browser by default the output will be like this:

Custom

But somethimes you just want to show some thing in your tests so there is a way to use a custom logger to show your tests any way you want.

var my_cool_logger = {
  "warn":   function(msg){},
  "log":    function(msg){},
  "info":   function(msg){},
  "error":  function(msg){
    alert(msg);
  },
};

scenario("Fancy scenario", {
  "somewhere over the rainbow": function(g){
    g.assert(false);
  }
}, my_cool_logger);

Backbone Atlas

2011-05-28T00:00:00-03:00

Backbone-Atlas is an extension for Backbone that provides a cleaner way of loading relations and data within any model. It does not overwrites Backbone.Atlas and helps in having chained relations.

In an ager for finding a cleaner way for working with Rails but in the client side I started to work with Backbone and realized that it provides a huge set of tools to create incredible rich client side applications.

One of the most common helpers to use within a ruby application is current_user and I'd really like to have something similar in my client application. So with that in mind I started to code.

Atlas provides attribute accessibility like ruby instead of using the .get(attr) from backbone. So instead of writing

      current_user.get('posts')

Now you can do this

      current_user.posts

There are some rules to make this extension to work. You must inherit from Backbone.Atlas.Model and you must be explicit in the key you want to use this is an example

      class @Post extends Backbone.Atlas.Model
        initialize: (attributes) ->
          @has attributes,
            comments: CommentList
            author: User

This will give you an author attribute to the model, initializated nil after creation, if loaded with json data will instance the model for the relation

      post = new Post({
        id: 1,
        title: 'Uber Title',
        author: {
          id: 29,
          name: 'Joe Doe'
        }
      })

Now accesible like this:

      post.id # => nil
      post.author # => User
      post.author.name # => Joe Doe

You can find more in Backbone Atlas with more examples. This is really simple but supports deep nesting of objects and relations.

In a few days a new version will be available, with npm support and internal identity map.

Having fun with QR codes

2011-05-20T00:00:00-03:00

I wanted to have a cool personal card but I wanted to be a little different and really geek-ish of course. So after some time thinking about the way i get some ideas and ane of them is this. A QR based card with some tweaking to make it appealing.

Inspired in this post i started the search for some library to create qr codes and thanks to the error correction i realized that i have more space in the QR than i thogth.

A lot of variations can be made and some ads are using this approach to get more people to photograph the qr codes. In my opinion this also helps to extend the social gap between a qr code and a bar code.

The Pretty QR library also gave me enoght help to create a really cool qr code and the result is fantastic. I'm starting to port it to Ruby so hopefully in some time i will be uploading it to github.

Cuba Libre chico

2011-05-12T00:00:00-03:00

I've been wandering in the Ruby world a year now, from Rails to Sinatra. But sometimes i'd really want things simpler and perhaps more clean of developing web applications. Specially when you can get something fast and get total control. Thats when i've found Cuba a great web framework.

In that spirit Cuba its a powerful web framework aiming simplicity, speed and clean syntaxt. Cuba inherits all its power from Rack and Rum but now overpowers it to make it even cooler. Being refactored some time ago now looks a lot like Sinatra routes, here's an example

require 'cuba'

Cuba.define do
  # /
  on "" do
    res.write "Home page"
  end

  # /users/:username
  on "users/:username" do |username|
    user = User.find_by_username(username)

    # GET /users/:username
    on get do
      res.write "Hello, i'm #{user.name}"
    end

    # POST /users/:username w/params[:user]
    on post, param('user') do |query|
      if user
        user.update_attributes query
        res.write "user: #{user.id} updated!"
      end
    end

  end

end

This encourages a cleaner and simpler way of writing routes, besides it also includes the power of Tilt

require 'cuba'

Cuba.define do
  on "register" do
    @message = "Hello dude!"
    res.write render("templates/register.erb")
  end
end

I liked Cuba so much i started a little lib to include all the contrib of Cuba, and i called it cuba-sugar

Which adds some things not so much, just to make writing a little easier following the way Cuba is doing stuff right now.

require 'cuba'
require 'cuba/sugar'

Cuba.define do
  on "faq" do
    # You can output the return of the block as the response
    as do
      "This are the most common questions"
    end
  end

  on "fancy" do
    @captcha = 123456
    as { render('templates/captcha.haml') }
  end

  on "coffee" do
    # And you can choose what HTTP code and extra headers
    as 419, {'Content-Type' => "text/teapot"} do
      "I DONT KNOW :(((("
    end
  end

  on "users/:username/json" do |username|
    user = User.find_by_username(username)
    as_json do
      {
        name:           user.name,
        location:       user.location,
        is_it_friday:   Time.now.friday?
      }
    end
  end

end

More than a Cubox way

2011-04-19T00:00:00-03:00

I know what you might think about writing something of the place you are actually working for, you might think that this is staged, payed for or even forced. You have all the possibilities in the world... and you will be wrong in any which.

This year will be my tenth aniversay of being working. Yep, 10 years, that's a lot of time, specially if you consider that my first official work was to clean a cybercafe. But don't take me the wrong way... i've loved each one of my jobs, i've learned a lot about being a professional, a teammate and a boss.

All my work experiences was pretty much the same: i go to the interview, some silly questions and go to work. I've met great people who teached me a lot.

And then i was one year ago, great paycheck, easy job and working in the core of great multinational powering a SMPP system. And one day that wasn't enoght, one day the work was not that fun, one day i saw myself in the same old spot, doing the same old thing.

Then a mail arrived, a friend of a friend was looking for someone to code Ruby. I only have C, PHP and Python as my everyday tools, but i take that chance. One small house in a common neighborhood, one cold basement as an enterview room and the thoghfest enterview i've ever faced. There was no psycologhist, no human resources guys... just badass developers with mad questions about the edge tech and things i've only read in wikipedia.

The truth is that i felt depressed after that enterview, i've felt that i was not enogh developer, that i needed to learn more... and i've loved that feeling. For the first time in years i realized that there's still much road to walk. I was really surprised when they mailed me to do pairing for a week. I really enjoyed to pair with all of them. I've learn about TDD, git secrets and to feel like part of a team.

The week was over and they made me an offer... less money than i was needed at the time and less guaranties. I was scared, just moved to a new apartament and a lot of debts in the credit cards. But things like this happen only once so i take the chance.

Months later we moved to a new house, bigger, lighter and in a better location. Founding myself surounded by coding ninjas increased my skills, my open source projects and my ability to grow. A relaxed enviroment with games, jokes and friends not only make me more productive also for the first time it makes me feel really part of something. They teached me about Scrum, Lean Startups and Agile Development. Cubox contributes OSS a lot and provides sponsorship if we want to. That's a big change from the places i used to work when you are just a number, just an asset.

When you work in a place where all the time you are being motivated with tech talks, retrospectives and even gifts. Yeah, we have T-shirts and new clothes :D. We do code reviews, debate with blankboards in every wall and talk everyday about the edge technologies in the world.

We play football, basketball and Paintball. We drink beers and go out. We also train together.

When you work with real friends and outstanding profesionals actually feeling like working is hard, at least to me. When you work the Cubox way you ofter forget the work part and just feel it like the only way of really enjoying everyday.

Migration to Github

2011-04-16T00:00:00-03:00

My journey starting over a blog in a way i really like. The quirks and things i must do to make this blog what it is today. So, after many years having (almost) a blog I've chose the best way of having one, using the incredible http://pages.github.com. I started the migration a few days ago and i found that for a developer like me having a git-powered blog is the only way to blog.

Just using the http://github.com/{username}/{username}.github.com repo will give you the ability of using static pages or Jekyll, the best way of managing a blog.

If you are curious about this blog, check it out here: elcuervo.github.com

The most amazing thing is the compatibility with different programming languages out of the box

puts "Go ruby!"

(defn test[a b] (println a))