Peace

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A normal bandage

I hate bandages. I really do. Everyone knows the best way for a wound to heal is to leave it exposed to oxygen and, hence, a bandage is the worst thing you can do to it.

A couple of days ago i took a big crash while going downhill on my bike (for gore lovers, check out the picture of my arm) and ended up with my right shoulder and elbow completely scratched. The elbow is a no brainer in the summer; since i use a t-shirt all day, it can just go around with Betadine on it and heal normally. The problem is the shoulder. Since i don’t usually like to use tank tops in my everyday life, it would be hard for my clothes not to get soaked in a mixture of blood and Bepanthene/Betadine.

Now, here’s an idea: why not create a bandage that is open everywhere, except in its boundaries – so that the wound can normally “breathe” and at the same time not be in contact with the clothes?

The bandage i needed

I kind had to pull a Mcggyver (check the last entry) and improvise one this morning. It works marvelously. I think i should start selling these things

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Ever since i heard about node.js i have been curious to try out one of these things. My ideas on it will come later but, for now, here are the required steps to make Sproutcore work well on OSX snow leopard. And i say work well because if you rely on the vanilla Ruby 1.8.7 that comes with snow leopard you will have a very crappy experience with Sproutcore; It will take approximately 35 seconds to reload any webpage every time you make a code change. And that will make you not want to use it at all.

Fortunately a lot of people have been kind enough to explain me, on twitter, how to make it faster.

But let’s start from the beginning:

1. Install Sproutcore using GEM, like so:

sudo gem install sproutcore

Note: I don’t remember if gem comes installed with snow leopard. If not, you can always google it

2. Follow the rest of the steps to setup your first application

By now you should have realized that (if you are using OSX snow leopard) the damn thing is freaking slow. So…

3. …download and compile the Ruby 1.9 source code for OSX

tar xzvf ruby-1.9.1-p376.tar.gz
cd ruby-1.9.1-p376
./configure --enable-shared --enable-pthread CFLAGS=-D_XOPEN_SOURCE=1
make
sudo make install

Note: The actual version could be different, as stuff evolves over time

4. Update the symbolic link on your system to point to the new ruby installation

sudo rm /usr/bin/ruby
sudo ln -s /usr/local/bin/ruby /usr/bin/ruby

5. Make sure the correct Ruby version is in use

ruby --version

Should return something like this:

ruby 1.9.1p376 (2009-12-07 revision 26041) [i386-darwin10.3.0]

6. Install thin. This server is faster than the one that comes with Sproutcore

sudo gem install thin

7. All done. Give it a try again

If you try to refresh the page of a Sproutcore example now you will notice the speed difference, like night to day. Have fun coding client-side desktop web applications

I’m planning to also take a look at Capuccino, another similar framework, but created in Objective-J – a derivative of Objective-C for javascript. Looks interesting and it might get me into iPhone development at last

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You can find the entire article here.

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So over the course of about 8 hours – the next day – we came up with bombthiscountry.com, a meaningless website where you can bomb any country in the world (yes, China, Tibet is a country). If you follow it on twitter you get daily statistics on the most bombed countries in the world.

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So I decided to give this a try and experiment a bit with it. This is my step by step process on getting a web page opening a websocket to a server and receiving the server’s date and time every second. It is based on an article by Joe Armstrong, though he uses Erlang for the server, while I decided to follow the easy road and use Google’s pywebsocket – an apache module (uses mod_python) that allows you to create handlers for websocket connections in a easy-to-use fashion. The code also contains a way to start a standalone server (i.e. not requiring apache) for testing purposes.

So here are the steps I took to get this working:

1. Create a web page

This is the code I borrowed from Joe, though slightly modified to fit my purposes (it requires jquery, by the way):

<html>

<head>

<script src="jquery-1.3.2.min.js"></script>
<script>

$(document).ready(function(){

var ws;

if ("WebSocket" in window) {
debug("Horray you have web sockets. Trying to connect...");
ws = new WebSocket("ws://localhost:9998/echo");

ws.onopen = function() {
// Web Socket is connected. You can send data by send() method.
debug("connected...");
ws.send("hello from the browser");
ws.send("more from browser");
};

run = function() {
var val=$("#i1").val(); // read the entry
$("#i1").val("");       // and clear it
ws.send(val);           // tell erlang
return true;            // must do this
};

ws.onmessage = function (evt)
{
//alert(evt.data);
var data = evt.data;
var i = data.indexOf("!");
var tag = data.slice(0,i);
var val = data.slice(i+1);
$("#" + tag).html(val);
};

ws.onclose = function()
{
debug(" socket closed");
};
} else {
alert("You have no web sockets");
};

function debug(str){
$("#debug").append("<p>" +  str);
};

});
</script>

</head>

<body>

<h1>Interaction experiment</h1>

<h2>Debug</h2>
<div id="debug"></div>

<fieldset>
<legend>Clock</legend>
<div id="clock">I am a clock</div>
</fieldset>

</body>

</html>

2. Download and install pywebsocket

Checkout the code with

svn checkout http://pywebsocket.googlecode.com/svn/trunk/ pywebsocket-read-only

Then do python setup.py build and sudo python setup.py install inside the src folder. This will install it into your python environment.

3. Being lazy, means we will change an example handler

The way pywebsocket works is delegating the connections to something they call handlers. In the pywebsocket-read-only/src/example folder you will find a file named echo_wsh.py. They have this convention where handlers are named <entry_point>_wsh.py. This means that when you later call (from your web page) the url http://localhost:9998/echo the server will delegate the processing of that connection to that file.

I modified that file to something like this:

# Copyright 2009, Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

from mod_pywebsocket import msgutil
from datetime import datetime
import time

_GOODBYE_MESSAGE = 'Goodbye'

def web_socket_do_extra_handshake(request):
 print 'Connected.'
 pass  # Always accept.

def web_socket_transfer_data(request):
 while True:
 time.sleep(1)
 date = datetime.now()
 #try:
 #    line = msgutil.receive_message(request)
 #except Exception, e:
 #    print 'Foi com os porcos'
 #    raise e
 #print 'Got something: %s' % line
 #msgutil.send_message(request, line)
 msgutil.send_message(request, 'clock!%s' % date)
 #if line == _GOODBYE_MESSAGE:
 #    return

So basically whenever a new connection is made to this entry point, a call to web_socket_do_extra_handshake is made. After that, web_socket_transfer_data is called and it’s your responsibility to create the loop that receives messages and handles the flow (as you can see in the commented lines). I don’t care about that right now, since I only want to push the date and time to the client every second.

3. Start the standalone server

Go to the pywebsocket-read-only/src/mod_pywebsocket folder and run the following command:

sudo python standalone.py -p 9998 -w ../example/

This will start the server in port 9998 and use the handlers directory specified by the -w option. That is where our echo_wsh.py lives.

4. Test it

So now open your browser (remember, only chrome supports websockets currently) and open the html file your created in the beginning. Voilá, server’s date and time every second in the clock div.

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