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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: email system. News server – news: newsgroups messages, used to be huge. Nic Shulver, [email protected] Intro: Developing Server Applications 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can be “asked” to run “service” programs Originally called Common Gateway Interface (CGI) applications, now largely superseded by FastCGI, SimpleCGI Apache plugins, Netscape NSAPI or Microsoft ISAPI Nic Shulver, [email protected] Intro: Developing Server Applications Servers: IIS,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 Nic Shulver, [email protected] 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 The modern replacements are much more efficient than the original CGI, yet still compatible. Nic Shulver, [email protected] Intro: Developing Server Applications 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. Nic Shulver, [email protected] Intro: Developing Server Applications 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 Nic Shulver, [email protected] 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, [email protected] 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, [email protected] 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 realtime, 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, [email protected] Intro: Developing Server Applications 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 Nic Shulver, [email protected] Intro: Developing Server Applications PHP – print all server variables PHP Variables Variable Value _SERVER["ALL_HTTP"] HTTP_CONNECTION:Keep-Alive HTTP_ACCEPT:*/* HTTP_ACCEPT_ENCODING:gzip, deflate HTTP_ACCEPT_LANGUAGE:en-gb HTTP_HOST:fcetdev1.student.staffs.ac.uk HTTP_USER_AGENT:Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET CLR 4.0.20506) HTTP_UA_CPU:x86 _SERVER["HTTPS"] off _SERVER["SCRIPT_NAME"] /wwwdata/nas1/DSAtest01/info.php _SERVER["HTTP_COOKIE"] no value _SERVER["AUTH_PASSWORD"] no value _SERVER["AUTH_TYPE"] no value _SERVER["AUTH_USER"] no value Nic Shulver, [email protected] 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, [email protected] Intro: Developing Server Applications 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 Nic Shulver, [email protected] Intro: Developing Server Applications 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) Nic Shulver, [email protected] Intro: Developing Server Applications 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) Nic Shulver, [email protected]