Nic Shulver, Intro: Developing Server Applications What is a server? Many types of server – File server – file: networked file space. FTP server – ftp: remote file space, often read-only. Web server – http: web pages and more. Mail server – mail: system. News server – news: newsgroups messages, used to be huge.

Nic Shulver, Intro: Developing Server Applications Web Servers Web servers used to be very simple: Accept requests for information, Respond with static HTML pages and graphics. Now servers can be “asked” to run programs on the server Originally called Common Gateway Interface (CGI) applications, now superseded by ISAPI/NSAPI. CGI/ISAPI/NSAPI programs use resources on the server to output information to the client browser.

Nic Shulver, Intro: Developing Server Applications Servers: IIS, Apache Internet Information Server Commercial server for Windows Comes with XP Pro on the install CD as an extra Apache ( Apache Free, open-source software Widely used, Linux/Unix/Mac/Windows support Easy to use on a stand-alone PC

Nic Shulver, Intro: Developing Server Applications Why “CGI”? Common - all server platforms use this standard. Gateway - controlled access to the server’s processing resources. Interface - client-server resource connector function. CGI - a method that allows data to be executed or interpreted instead of just delivered and displayed. NB Modern ISAPI/NSAPI is much more efficient than the original CGI.

Nic Shulver, Intro: Developing Server Applications HTML vs. CGI “ This reference asks the server (Gawain) to look in the (shortcut to the) cmtnas directory and find a file called “homepage.htm”. The simple server knows that.htm and.html files are HTML and must be sent, without further processing, to the browser. Some servers also check for “commands” inside the HTML – often SSI, “server-side includes”.

Nic Shulver, Intro: Developing Server Applications HTML vs. CGI This reference asks the server (fred.co.uk) to look in the (shortcut to the) scripts directory and find a file called “debug.php”. The server knows that a.php file is a page with embedded script and must be executed by the Web server software as a sub-process. Any output from running the script is sent to the browser.

Nic Shulver, Intro: Developing Server Applications CGI+ languages Web server programming can be accomplished using many suitable languages. Popular ones are; Modern: PHP (.php), VBScript or JScript (in ASP,.asp), ASP.NET (.aspx) Java Server Pages (.jsp) Old CGI: perl (.pl), C, C++, any “normal” programming language (.exe)

Nic Shulver, Intro: Developing Server Applications PHP PHP means “PHP Hypertext Pre-processor” (sic). Originally it was known as “Personal Home Pages” but that is poor for marketing as a business solution! It was also called “perl Hypertext Pre-processor” but PHP is no longer just a web-version of perl. The PHP language is a mixture of C, perl and others. PHP is supported on many platforms (Mac, PC, Linux…).

Nic Shulver, Intro: Developing Server Applications What’s it for? A plain HTML document that the Web server delivers is static, which means it doesn't change. A CGI program, on the other hand, is executed in real- time, so that it can output dynamic information. CGI allows someone visiting your Web site to run a program on your machine that performs a specified task – maybe updating a weather report or grabbing a digital photo. E-Commerce, blogs, web services, discussion areas… many use PHP.

Nic Shulver, Intro: Developing Server Applications PHP – print all server variables All $_SERVER settings <?php foreach($_SERVER as $key=>$sItem) {echo "$key = [$sItem] \n"; } ?>

Nic Shulver, Intro: Developing Server Applications Example Script Output (fragment) SCRIPT_NAME = [/phpTest/test.php] QUERY_STRING = [] REMOTE_USER = [DEXTER\nic] REQUEST_METHOD = [GET] SERVER_PORT = [80] SERVER_PROTOCOL = [HTTP/1.1] SERVER_SOFTWARE = [Microsoft-IIS/5.1] REQUEST_URI = [/phpTest/test.php] URL = [/phpTest/test.php] SCRIPT_FILENAME = [c:\inetpub\wwwroot\phpTest\test.php] ORIG_PATH_INFO = [/phpTest/test.php]

Nic Shulver, Intro: Developing Server Applications Raw CGI data - encoding Information is sent from a form to a script in a very odd format. If field “name” has the value “G Singh”... and “job” has the value “principal lecturer”... the script will receive the string “name=G%20Singh&job=principal%20lecturer”. But PHP splits this up for you and makes it easy to use, so you don’t usually worry about it.

Nic Shulver, Intro: Developing Server Applications Summary We have briefly met different types of server. We have discussed the reasons for needing CGI+. … and contrasted plain HTML with dynamically created content. We have noted the wide range of CGI+ languages in use on the Internet. … and looked at a specific language, PHP. We have briefly considered standard URL-encoded parameters.