But what is a User Agent? A User Agent is the client application used with a particular network protocol; the phrase is most commonly used in reference to those which access the Web. Web user agents range from web browsers and e-mail clients to search engine crawlers (spiders), as well as mobile phones, screen readers and braille browsers used by people with disabilities. When Internet users visit a web site, a text string is generally sent to identify the user agent to the server. This forms part of the HTTP request, prefixed with user-agent: and typically includes information such as the application name, version, host operating system, and language. Bots, such as web crawlers, often also include a URL and/or e-mail address so that the webmaster can contact the operator of the bot.

By simply typing about:version into Chrome’s address bar you will be presented with the following information:

Google Chrome
0.2.149.29 (1798)
Official Build
Google Inc.
Copyright © 2006-2008 Google Inc. All Rights Reserved.
Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/0.2.149.29 Safari/525.13

As you can see Chrome’s version information provides limited detail about the browser. The last line is the important one. It is the HTTP User-Agent header:

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/0.2.149.29 Safari/525.13.

If you know the RFC 2616 specification on the HyperText Transfer Protocol — which incidentally, I gladly don’t — you would know that the User Agent, or more formally, product token, should be short and to the point:

Product tokens SHOULD be short and to the point. They MUST NOT be used for advertising or other non-essential information. Although any token character MAY appear in a product-version, this token SHOULD only be used for a version identifier (i.e., successive versions of the same product SHOULD only differ in the product-version portion of the product value).

Clearly this isn’t the case! One of Google’s reason’s behind creating the Chrome browser was to start afresh. It would have therefore been truely amazing if they had made the string simply Chrome/0.2.149.27.

Unfortunately, browser sniffing makes an ever-growing UA string the path of least resistance for browser vendors.

So, what does Chrome’s User Agent string actually mean:

• Mozilla/ – This means that browser has the kind of capabilities that Netscape 1.1 had compared to Mosaic and Lynx.
• 5.0 – This means that the browser engine is from the post-Browser War Web Standards era as opposed to being from the Browser War era.
• (Windows; – This means that general windowing system flavor the browser runs on is Windows (as opposed to, for example, Apple and X11).
• U; – This means that the browser has at least the level of cryptographic capability / encryption strength that U.S. versions of browsers had in the late 1990s.
• Windows NT 6.0; – This indicates the operating system the browser is running on. In this instance, the browser is running on Vista.
• en-US) – This indicates the user interface language of the browser (U.S. English in this case). This may be used to choose between different content languages even though HTTP has a different header for that purpose.
• AppleWebKit/ – This indicates that the engine of the browser is WebKit as opposed to being Gecko. Developers should not do user agent sniffing as a rule, but if they still do, this is what they should be sniffing.
• 525.13 – This is the WebKit version from which Chrome branched its copy. Site admins could use this to detect old versions with known bugs.
• (KHTML, like Gecko) – This introduces the substring Gecko into the UA string while pointing out to human readers that Webkit was forked from KHTML. Without this substring, Chrome might be put in the same category as IE and Netscape 4.
• Chrome/ – This string identifies the browser as actually Google Chrome.
• 0.2.149.27 – This is the Chrome version. This could be used to detect old versions with known bugs.
• Safari/ – This means that the browser is like Safari as opposed to being like Firefox.
• 525.13 – This just repeats the WebKit version in order to have some version but not the irrelevant Safari.app version.

So what is the big deal? The Adobe marketing team state that:

The Adobe AIR runtime lets developers use proven web technologies to build rich Internet applications that deploy to the desktop and run across operating systems. Adobe AIR offers an exciting new way to engage customers with innovative, branded desktop applications, without requiring changes to existing technology, people, or processes.

What AIR applications should you check out?

What is intriguing is that all the tools I have chosen are generally useful tools for the developer or designer, with the exception of twhirl, which is a social-interaction tool. I’m looking forward to when other, less developer-centric tools become freely available. AgileAgenda has taken the lead with this respect, albeit not freely available, as has eBay desktop, but I would like to see examples from the BBC in the form of a desktop BBC iPlayer or maybe a Flickr image browser, del.icio.us bookmark reader, RSS aggregator and a Picnik image editor.

Analytics Reporting Suite

The Analytics Reporting Suite, by Nicolas Lierman, brings Google Analytics to the desktop. It uses it’s own custom API to interact with Google and nearly implements all the features of Analytics.

For website owners this is a must-have application. Like the twhirl AIR application below, it is a fantastic example of what can be achieved with Flex and AIR. Measuring visitor trends and traffic are essential tasks to managing and improving a websites performance. The Analytics Reporting Suite allows you to configure multiple Google’s Analytics accounts and access the web-based suite’s plethora of features via a desktop application. The application displays integrated graphs and animations via a tabbed interface, which allows you switch between a number of reports. These reports can then be saved as a PDF, Excel or XMLdocument, or printed.

You can download and install the application from the About Nico website.

twhirl twitter Client

twhirl, by Marco Kaiser, is probably the most popular desktop client for the twitter micro-blogging service. Most of the features available on the twitter website are accessible through twhirl, plus, a lot of usability enhancements have been added to make it easier to manage multiple accounts. This is great for those who want to separate business and personal accounts they may have.

The twhirl application is a great example of how AIR can bring web applications to the desktop; it can dock to the system tray, display message alerts and you can configure the applications opacity when not focused (great if you like Mac and Vista-styled themes). The application allows you to search twitter users, view their timelines, add friends, view followers, delete tweets and much much more. Twhirl automatically fetches your friends’ status updates, direct messages and replies, whilst also colour coding different types of messages and alerting you to messages both audibly and visually.

The twhirl application is skinnable and comes with several built in skins with which you can customise the application. All-in-all twhirl is not only one of the best twitter clients, but AIR applications.

You can download and install the application from the twhirl website.

Kuler Desktop

Adobe kuler is the first web-hosted application from Adobe Labs designed both to stand alone and to complement Adobe Creative Suite software. Built using Adobe Flash and ActionScript 3.0, kuler is all about colour: colour for exploration, inspiration, experimentation and sharing. Kuler is clearly targeted at the designer, but anyone interested in colour will benefit from its use.

You can download and install the application from the Adobe Labs website.

WebKut

WebKut is a web screenshot tool that allows you to capture web pages, or parts of them in a very simple way. It provides you with 3 capture options: the entire page, the current view, or only a selection. This little application proves particularly handy for those presentations or projects that need great visuals from the web.

You can download and install the application from the WebKut website.

RichFLV

RichFLV, by Benjamin Dobler, lets you edit FLV files. The key features include reading FLV metadata, read and edit cuepoints, cut FLV files, convert the sound from an FLV to MP3 format, convert an FLV to an SWF … and much more.

You can download and install the application from the Adobe AIR Marketplace website.

SearchCoders Dashboard

This Flex-based chat widget is designed with programmers in mind. The code input feature allows developers to chat about code without disrupting the conversation.

You can download and install the application from the SearchCoders website.

Pownce

Much like twhirl in look, feel and ease-of-use, but with a slant towards productivity rather than micro-blogging, Pownce is a way to keep in touch and share things with your friends or colleagues. You can send people files, links, events, and messages and then have real conversations with the recipients. This is a great collaboration tool and was one of the first services to really embrace AIR as an application architecture, which could realise their service as a desktop client. Everything that is available via the Pownce website is also available via the client application, except and possibly importantly, the ability for the user to amend their account settings and add friends to your network; this still has to be done via the website.

For a small annual amount, Pownce offers a paid-for service which will eliminate adverts from your profile and allow you to send huge file sizes (100MB) and customise the theme of your Pownce.

Pownce also offers Drupal integration and a mobile application, which works with the iPhone, BlackBerries and many more ‘internet-ready’ mobile devices.

You can download and install the application from the Pownce website.

Only one usage of each socket address (protocol/network address/port) is normally pemitted.
make_sock: could not bind to address 0.0.0.0:80
no listening sockets available, shutting down
Unable to openlogs
Note the errors or messages above, and press the < ESC > key to exit.

Initially I thought it was a problem associated with Windows Vista (yes my development machine is a Vista PC!) and the previously installed IIS. However, after a lot of deliberating and Google searches, it appears that Skype was the culprit. Skype listens on port 80 and 443 for incoming requests. So to solve the problem I simply closed down Skype and re-installed Apache. As Apache was setup as a Windows service, no conflicts subsequently arise with Skype as Apache will start using the ports before Skype.

There is a setting in Skype under Tools > Options > Advanced > Connection called “Use port 80 and 443 as alternatives for incoming connections”. This is checked by default. Uncheck this to prevent conflicts with Apache.

The Key Point: Stop Skype before installing Apache.

The task I was trying to achieve was the installation of development versions of WordPress, Drupal, MediaWiki and Moodle, all of which would require a MySQL database. Trying to load the MySQL extension should have been a simple case of uncommenting the line in the php.ini and restarting the Apache service. With Vista, this was certainly not the case.

I set up a very simple page detailing the php configuration in an index.php file:

< ?php phpinfo(); ?>

This showed me the default configuration path of my php.ini and extensions directory, amongst a whole host of other information.

In both cases the paths were incorrect. First and foremost the configuration file path stated C:\Windows when in fact I had installed it in the root (C:\PHP5). So, although I was amending the php.ini file with the correct detail, Vista was using the default values. If there is no php.ini file in Windows, then you’ll continue banging your head against a brick wall.

The problems didn’t stop there. Moving the php.ini file to the Windows directory under Vista isn’t a simple copy and paste task. You need to be administrator. But Vista’s administrator priviledges are more pseudo than actual! In order to amend and save the php.ini file in the Windows directory, you must run Notepad as administrator and save the file as such. Voila! Everything then works. The phpinfo() function returned the correct installation detail and I could continue with the job I was meant to be doing.

PS. Thanks to Rob Douglas for his help.