1. MSc Internet Computing
CSYM010
Server Side Software
Lecturer: Espen Svennevik

2. Content Web Servers Common Gateway Interface
Server side scripting languages

3. Scheme of work Tuesday 7th Feb
Webservers, CGI & server side scripting languages- PHP
14th Feb
PHP
21st Feb
PHP & MySQL
28th Feb
7th March
JSP & JDBC or AJAX
14th March
ASSIGNMENT
21st March
ASSIGNMENT – Hand into AHO by Friday 25th March
Easter Break

4. Webserver Apache - Multiplatform Microsoft IIs Jakarta Tomcat
HTTP Protocol
Typically TCP Port 80

5. HTTP HyperText Transaction Protocol Version 1.0 or 1.1
Simple text based protocol
Client requests
Server responds (possibly with an error)

6. HTTP continued - Example
Client:
GET /~espen/CSYM010/test.html HTTP/1.0
Server:
HTTP/ OK Or
HTTP/ Not Found

7. HTTP continued - Example
espen:~ espen$ telnet 80
Trying
Connected to my23-1.eng.nene.ac.uk.
Escape character is '^]'.
GET /~espen/CSYM010/test.html HTTP/1.0
HTTP/ OK
Date: Tue, 07 Feb :36:14 GMT
Server: Apache/ (Unix) PHP/4.3.10
Last-Modified: Tue, 07 Feb :36:15 GMT
ETag: W/"90db db300"
Accept-Ranges: bytes
Content-Length: 22
Connection: close
Content-Type: text/html
X-Pad: avoid browser bug
<b><i>CSYM0101</i></b>Connection closed by foreign host.
espen:~ espen$

8. HTTP continued Common status codes 200 OK
The request succeeded, and the resulting resource (e.g. file or script output) is returned in the message body.
404 Not Found
The requested resource doesn't exist.
301 Moved Permanently
302 Moved Temporarily
303 See Other (HTTP 1.1 only)
The resource has moved to another URL (given by the Location: response header), and should be automatically retrieved by the client. This is often used by a CGI script to redirect the browser to an existing file.
500 Server Error
An unexpected server error. The most common cause is a server-side script that has bad syntax, fails, or otherwise can't run correctly.

9. HTTP continued Other methods apart from GET are: POST - Similar to GET
HEAD - Gets header only - no body

10. Common Gateway Interface (CGI)
Interface to server side scripts
Client (browser) request a script
Server executes scripts
Output of scripts are returned to the client
Client (browser) displays (renders) output

11. CGI Example Written in UNIX shell #!/bin/sh
echo "Content-Type: text/html"
echo
NOW=`date`
echo "<h1>Todays date and time is $NOW</h1>"

12. CGI Example - continued
Output
Content-Type: text/html
<h1>Todays date and time is Tue Feb 7 11:48:09 GMT 2006</h1>

13. Second CGI example #!/bin/sh echo "Content-Type: text/html” echo
for i in do
echo "<h$i>Header $i</h$i>”
done

14. Second CGI example - cont’
Content-Type: text/html
<h1>Header 1</h1>
<h2>Header 2</h2>
<h3>Header 3</h3>
<h4>Header 4</h4>
<h5>Header 5</h5>
<h6>Header 6</h6>

15. Apache environment variables
Apache passes data to scripts in environment variables. These include:
DOCUMENT_ROOT="/var/www/html”
GATEWAY_INTERFACE="CGI/1.1"
HTTP_ACCEPT="image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, image/png, */*”
HTTP_ACCEPT_CHARSET="iso ,*,utf-8”
HTTP_ACCEPT_ENCODING="gzip"
HTTP_ACCEPT_LANGUAGE="en”
HTTP_CONNECTION="Keep-Alive"
HTTP_HOST=" ”
HTTP_USER_AGENT="Mozilla/4.74 (Macintosh; U; PPC)”
PATH="/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin”
QUERY_STRING=""
REMOTE_ADDR=" "

16. Environment variables
REMOTE_PORT="1740"
REQUEST_METHOD="GET”
REQUEST_URI="/cgi-bin/printenv”
SCRIPT_FILENAME="/var/www/cgi-bin/printenv”
SCRIPT_NAME="/cgi-bin/printenv”
SERVER_ADDR=" ”
SERVER_NAME="radon”
SERVER_PORT="80" SERVER_PROTOCOL="HTTP/1.0”
SERVER_SIGNATURE="<ADDRESS>Apache/ Server at radon Port 80</ADDRESS>\n”
SERVER_SOFTWARE="Apache/ (Unix) (Red Hat/Linux) mod_ssl/2.6.6 OpenSSL/0.9.5a DAV/1.0.1 PHP/4.0.2 mod_perl/1.24"

17. CGI script & environment
#!/bin/sh
echo "Content-Type: text/html”
echo
echo "<h1>Your browser is $HTTP_USER_AGENT</h1>”
echo "<h2>Your IP address is $REMOTE_ADDR</h2>”
echo "<h2>Your PORT number is $REMOTE_PORT</h2>"

18. CGI script & environment
• Previous script produces this output in the browser window:
Your browser is Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv: ) Gecko/ Firefox/
Your IP address is
Your PORT number is 51046