World Wide Web WeeSan Lee

Roadmap Introduction HTTP URL HTML CGI Apache Server Installation Squid Cache Server Q&A

Introduction Invented by Tim Berners-Lee in 1989/1990 Client-server architecture Servers  Apache, Netscape Enterprise Server, MS IIS, etc Clients  GUI Mosaic, Netscape, Mozilla, Firefox, Opera, Konqueror, Epiphany, IE, Safari, etc  Text Link, wget, emacs, telnet, etc

HTTP Hypertext Transfer Protocol Listen on port 80 or http (/etc/services)  $ grep " 80/tcp" /etc/services http80/tcp www RFC2068 defines HTTP/1.0 RFC2616 defines HTTP/1.1 Built on top of TCP

HTTP (cont) $ telnet 80 Trying Connected to Escape character is '^]'. GET / HTTP/1.0 HTTP/ OK Date: Mon, 16 Jul :47:38 GMT Server: Apache/2.2.3 (CentOS) Last-Modified: Mon, 16 Jul :08:44 GMT ETag: "889f0f-d5-71bab00" Accept-Ranges: bytes Content-Length: 213 Connection: close Content-Type: text/html; charset=UTF-8 …

URL Uniform Resource Locator Eg.   http – protocol/application  – hostname  80 – port  ~weesan/ - directory  Index.html - filename

URL (cont) Other protocols  file file://etc/passwd  ftp ftp://ftp.slackware.com/pub/slackware/slackware-12.0/  https  mailto

HTML Hypertext Markup Language Eg.  A sample HTML  Me

CGI Common Gateway Interface A way to communicate with external programs and generate pages dynamically Example of external scripts/programs:  Perl, PHP, Python, Ruby, Bash, C/C++, Cobol, etc Servers support plugins for performance, eg.  libphp4.so  libphp5.so  libperl.so

Apache Server Installation $ yum install httpd Files are distributed all over the places  /etc/httpd/conf/httpd.conf  /usr/sbin/httpd  /usr/sbin/apachectl  /var/www/html/  /var/www/cgi-bin/  /var/log/httpd/access_log  /var/log/httpd/error_log

Apache Server Installation (cont) To start the httpd server  $ /etc/init.d/httpd start To restart the httpd server  $ /etc/init.d/httpd restart To stop the httpd server  $ /etc/init.d/httpd stop To start the httpd server on reboot  $ chkconfig --level 2345 httpd on

Squid Cache Server A free version spawned from Harvest Cache Project from USC, which became NetCache, and 8 months later, it was acquired by NetApp Caches objects locally  Saves bandwidth  Reduces latency Fast, not process forking for new connections Supports Hierarchy Caching Listen on port 3128

Squid Cache Server (cont) $ telnet cache.cs.ucr.edu 3128 Trying cache.cs.ucr.edu... Connected to cache.cs.ucr.edu. Escape character is '^]'. GET HTTP/1.0 Host: HTTP/ OK Date: Thu, 08 May :11:19 GMT Server: Apache/2.2.3 (CentOS) X-Powered-By: PHP/5.1.6 Content-Type: text/html; charset=UTF-8 X-Cache: MISS from cache.cs.ucr.edu Via: 1.0 cache.cs.ucr.edu:3128 (squid/2.6.STABLE14) Proxy-Connection: close …

Squid Cache Server (cont).com.edu.net GET HTTP/1.0http://

Squid Cache Server (cont) Accelerator Mode  Reverse Proxy  To make web server faster for static pages Transparent Caching  Uses iptables  Configuration-free from clients

Squid Cache Server (cont) To create swap directories  $ squid –z  Run only once!!! To run Squid Cache Server  $ RunCache To reload the configuration  $ squid -k reconfiguration To rotate the log files  $ squid -k rotate

Reference LAH  Ch 21: Web Hosting and Internet Servers Apache Web Server  Squid Cache Server 