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CS120 Lecture 17a:
Publishing Web pages
John Magee
9 November 2012
1
Overview/Questions
– So I got some HTML pages and stuff. How do
I make them show up on the web?
– What are web servers, anyway?
– How do we transfer files to a web server?
– Who can see my pages?
– URLs, absolute path, and relative path
revisited.
2
How to Publish a Web Page
Create HTML document, locate ancillary
files (e.g images).
 Transfer files to web server
 Set permissions for read access
 Test the URL in your browser

3
Recall: Displaying a WWW Page
4
What’s a Web Server?
Is it hardware?
 yes!
Is it software?
 yes!
How is it both?
What hardware is needed?
What software is needed?
5
What’s a Web Server?
Web server: a software application which
waits for /responds to HTTP requests.
Tim Berners-Lee wrote 2 applications to
make the web:
– A web browser called WorldWideWeb
– A server called HTTPd
6
The first WWW Server at CERN.
What’s a Web Server?
Today’s web servers use
high-performance
hardware like this:
(fast network and disk
access)
Pictured: IBM Blade Servers hosting
files.myopera.com, photo from Wikipedia
7
What’s a web server?
The Apache HTTP Server is the most
popular web server (since 1996).
Roles:
– Processing HyperText Transfer Protocol
– Logging
– Delivering static content from the file system
– Running scripts to deliver dynamic content
8
LAMP Model
The most common structure for web applications
uses this configuration:
Linux operating system for a server
Apache web server software
MySQL database software
PHP/Perl/Python scripting language to create
dynamic HTML
9
How a Web Server Works
Receives HTTP Request
 Search for resource (file) on disk
 Send HTTP Response (status code + data)

– If not found: status 404 (NOT FOUND)
– If not permitted: status 403 (FORBIDDEN)
–…
– Else: status 200 (OK) + send data
10
cs-people.bu.edu
Our WWW server is www.cs.clarku.edu.
The web server has a file system which it
searches for a URI (resource pathnames).
– Subdirectories for individual users:
 http://www.cs.clarku.edu/<username>
– Example:
 http://www.cs.clarku.edu/~jmagee
11
Your UNIX Home Directory
With the CS UNIX account, each user has a
“home” directory:
General form:
/home/<username>/
Example:
/home/jmagee/
This has a UNIX pseudonym of ~.
12
Your WWW Directory
The web server will map this URL:
http://www.cs.clarku.edu/~<username>/
to your CS UNIX’s account’s
~/public_html/ directory
13
Locate files in
Finder/Windows Explorer
Find your files on your local computer
14
How to Transfer Files
to csgateway.clarku.edu
Use a file transfer client-program:
– Fetch (Mac)
http://fetchsoftworks.com/
(a free academic license is available)
– WinSCP (Windows)
http://winscp.net/eng/index.php
(also free)
- SSH Secure Shell (Windows)
15
Connecting by WinSCP:
– Hostname: csgateway.clarku.edu
– Be sure to use the “SFTP” protocol
16
WinSCP to csa2.bu.edu
After you
connect,
transfer files
by drag’n’drop.
Then rightclick to set
permissions.
17
File Permissions
File Permissions
Each file has its own set of permissions for:
– Reading, writing or executing
– Owner, group, or others
– This leads to a 3x3 matrix of permissions:
18
Setting Permissions by WinSCP

Right-click to open this dialog

Set the permissions to 644
19
Transferring File by Fetch

Use drag’n’drop interface to transfer files…

Then use the Get Info button to set permissions.
20
Setting Permissions by Fetch

Set permissions to 644
21
Testing the Webpage:
After uploading the files, test in your
browser:
There are two special filenames that the
web server looks for automatically:
– home.html
– index.html
22
Take-Away Points
– Web server
– UNIX home directory
– File Transfer Protocol
– UNIX File Permissions
23