1 / 15

What is a server?

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: email system. News server – news: newsgroups messages, used to be huge. Web Servers.

angelo
Download Presentation

What is a server?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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: email system. • News server – news: newsgroups messages, used to be huge.

  2. Web Servers • Web servers used to be very simple: • Accept requests for information, • Respond with static HTML pages and graphics. • Servers can be “asked” to run “service” programs • Originally called Common Gateway Interface (CGI) applications, now largely superseded by • FastCGI, SimpleCGI • Apache plugins, • Netscape NSAPI or Microsoft ISAPI

  3. Servers: IIS, Apache • Internet Information Server (24.5%, Mar 2010) • Commercial server for Windows • Came with XP Pro on the install CD as an extra • Also available with Vista and Windows 7 • Apache (54.5%, Feb 2010) • Free, open-source software • Widely used, Linux/Unix/Mac/Windows support • Easy to use on a stand-alone PC

  4. 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 The modern replacements are much more efficient than the original CGI, yet still compatible.

  5. HTML vs. CGI • “http://www.fcet.staffs.ac.uk/nas1/homepage.htm” • This reference asks the server (fcet) to look in the (shortcut to the) nas1 directory... • ... and find a file called “homepage.htm”. • The simple server knows that .htm and .html files are HTML • It sends the files, without further processing, to the browser. • More complex servers can do much more.

  6. HTML vs. CGI • http://fred.co.uk/scripts/debug.php • This reference asks the server (fred, a commercial server in the 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 run by the Web server software in a special way • Output from the script is sent to the browser

  7. 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)

  8. 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…).

  9. 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.

  10. PHP – print all server variables • <?php • phpinfo(32); • ?> • This looks suspiciously simple! • PHPinfo() is a built in function that reports all sorts of information • The “32” tells the function to show us the values of the server variables

  11. PHP – print all server variables

  12. 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.

  13. Summary • There are 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

  14. References (Checked: Aug 2010) • Common Gateway Interface(http://en.wikipedia.org/wiki/Common_Gateway_Interface) • Apache HTTP Server(http://en.wikipedia.org/wiki/Apache_HTTP_Server) • The Apache HTTP Server Project(http://httpd.apache.org/ABOUT_APACHE.html) • MS Internet Information Services(http://en.wikipedia.org/wiki/Internet_Information_Services) • The Official Microsoft IIS Site(http://www.iis.net/overview)

  15. References (Checked: Aug 2010) • PHP(http://en.wikipedia.org/wiki/Php) • PHP: Hypertext Preprocessor(http://www.php.net/) • MySQL, the world's most popular open source database(http://www.mysql.com/?bydis_dis_index=1)

More Related