Category: Programming

Simple Local Web servers November 27th, 2013

I’ve had this post saved as a draft for two years, so I finally decided to clean it up a little and publish it in case anyone else finds the information useful.

In web development, for both client and server testing, it’s often very useful to have a local web server running in order to serve test cases. This post outlines a few quick and easy ways to run a local web server that don’t involve installing Apache or nginx and all their dependencies.

The simplest way I know of to get a local web server is with netcat:

brandon@dexter:~$ nc -l 8000

Then, when you hit the URL http://localhost:8000 in your browser, you will see the request show up on the terminal where netcat is running:

GET / HTTP/1.1
Host: localhost:8000
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:6.0a1) Gecko/20110513 Firefox/6.0a1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Cache-Control: max-age=0

You can then type an arbitrary response back to the browser, terminating the stream with Ctrl+C:

HTTP/1.1 200 OK
Content-Type: text/html

Hello <b>world</b>

The hello world HTML page shows up in your browser as you would expect. You could just as easily use an existing file on your filesystem as input for the response:

brandon@dexter:~$ nc -l 8000 < http_response_file.txt

Another option to consider, especially if you already have test cases or other static content ready to serve, is Python’s SimpleHTTPServer class. You don’t even need to write a script to run one of these servers locally:

brandon@dexter:~$ python -m SimpleHTTPServer 8000
Serving HTTP on port 8000 ...d

This time, hitting http://localhost:8000 in your browser will bring up a directory listing with your current working directory as the document root. Your requests are also logged on your Python terminal:
localhost - - [16/May/2011 14:55:36] "GET / HTTP/1.1" 200 -

On a separate but related note, you can get a local SMTP testing server, which only logs to the console and doesn’t actually send mail, by running:

$ sudo python -m smtpd -c DebuggingServer -n localhost:25

---------- MESSAGE FOLLOWS ----------
Content-Type: multipart/alternative;
MIME-Version: 1.0
Subject: Veracode report for 2013-10-24

Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit

= Plain text version =
Hello world!

Content-Type: text/html; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit

<h1>HTML Version</h1>
<p>Hello <b>world</b>!</p>

------------ END MESSAGE ------------

Standing on the Shoulders of Giants October 15th, 2013

I recently created a new theme for my personal site*, and was struck anew by how many Open Source Software packages this site is built on top of.  To name a few of the essential ones:

In other words, every layer of the Web stack, which I use every day for fun and for profit, is powered by Open Source Software.  It would be beyond impossible to deploy a website today with rich, interactive experiences without these fundamental pillars.  I owe so much to Linux, Open Source, and Open Standards, and it is only right that I acknowledge this fact.

* Many thanks, also, to David Goines, who graciously allowed me to use his artwork in the new site design.

Moving to GitHub March 8th, 2011

GitHub is an amazing tool which holds a lot of promise for pushing open source software development forward. I say that because they make the process of forking someone else’s repository and then merging your changes (with their permission, of course) back into the master repo as simple as a few mouse clicks. I, for example, contributed a patch that made jQuery CSP-compatible which was later pulled into the jQuery trunk.

Since GitHub has become the industry standard for sharing code, I’ve started the process of moving all of my open source tools to a repository there. So far, I have only moved my Python CIDR block converter, but the rest should follow soon!

Productivity music for work September 8th, 2010

There are times at work when I like to put on my headphones and play some music (usually instrumental) or white noise to avoid distraction while I write code or do some other task that requires concentration. I never thought to do both at the same time… until now!

Next time you want a nice anti-distraction music cocoon try opening in separate tabs:

  1. A nice Jazz Piano or Classical station
  2. A pleasant rainfall soundtrack

If you are still distracted after that Google has some information that might help you.

Jetpack: Unread Messages in Gmail App Tab August 13th, 2010

One of the new features in Firefox 4 is the App Tab which lets users persist a tab that they use continuously. Firefox shrinks the tab down to just the favicon and places it in a special area for these tabs which generally aren’t closed by the user. The feature is great, but one of the side effects is that Gmail App Tabs don’t show anymore the part of the <title> that indicates unread messages.

That’s where my new Jetpack (a cool new, lightweight (and secure!) way to write Add-ons) comes in.

Go install Unread Gmail Favicon from AMO and the favicon for that tab will indicate the number of unread messages when you have them like so:

Hacked my DEF CON 18 badge July 30th, 2010

I was only able to stay for part of the first day of DEF CON this year, but I’m glad I did. One of the things they’ve done for the last five years or so is put microcontrollers in the badges, and put in little Easter eggs for people to search for. This year’s had a Ninja Party mode which was locked by default, but you could unlock it by placing a series of 15 tumblers in the correct position.

They published the source code for the badges on the CD they gave out at registration (so perhaps I’m stupid for loading the CD on my laptop rather than smart for reverse engineering the badge). I opened up DC18_Badge.c and, searching for “Ninja” (the code was commented nicely), quickly found the following two C functions:


int dc18_ninja_validate(uint32_t val) 
    uint16_t a, b;
    a = (uint16_t)(val & 0xfff);
    b = (uint16_t)(val >> 12);
    if((a ^ b) == 0x916) 
        return 1;
    return 0;

// encode tumbler states into
// 24-bit value
    uint32_t x = 0, j = 1;
    uint16_t i;
    for (i = 0; i < TUMBLERS_PER_IMAGE;
        x += tumblers[i] * j;
        j *= 3;
    return x;

So the trick was to find the number that made (a ^ b) == 0x916 and then figure out the tumbler positions to represent that number. I wrote two small Python functions to automate those tasks. To find the number that would unlock Ninja Mode, I wrote this loop. I added a print statement to show how far into the search we were, thinking it might take some time to find it, but it popped out 6423 in no time at all:

while 1:
    a = i & 0xfff
    b = i >> 12
    if i % 10000 == 0:
        print "# a: %d, b: %d, i: %d" % \
            (a, b, i)
    if a ^ b == 0x916:
        print "DONE: %d" % (i)
    i += 1
DONE: 6423

Now all that was left was to figure out the tumbler positions to represent 6423. Clearly, dc18_encode_tumblers tells us how to do that. I whipped up this little function to convert the tumbler positions to a decimal number:

def enc_tumblers(tum):
    x = 0; j = 1;
    for i in range(15):
        x += tum[i] * j
        j *= 3
    return x

>>> enc_tumblers([1,1,1,1,1,2,2,2,

I was going to write another loop to increment the tumbler array I was passing to enc_tumblers, but my first guess was so close that I just manually entered the settings until I found the winning configuration:

>>> enc_tumblers([0,2,2,0,1,2,2,2,

Once I had the configuration, I put the tumblers in the appropriate positions: 0 - up, 1 - middle, 2 - down. After that, well, I guess I'm a ninja now:

East Bay Psychotherapist
Licensed Clinical Social Worker provides psychotherapy and counseling services for couples and individuals in the East Bay Area.