HTTP

title

HTTP

author

Sam Bashton (NobleProg Ltd)

HTTP ⌘

• Stateless, no support for sessions
• A single TCP connection is created per request

• For HTTP 1.0, multiple requests can be 'pipelined' in 1.1

HTTP Requests ⌘

A very simple HTTP request ⌘

`GET / HTTP/1.0`

HTTP Virtual Hosting ⌘

• Imagine we wish to host www.example.com and www.example.es on the same server
• HTTP 1.0 requires that every website has a unique IP
• This is massively wasteful of IPs, as well as requiring extra administration
• Solution: HTTP/1.1 and virtual hosts

A simple HTTP 1.1 request ⌘

• GET / HTTP/1.1
• Host: www.example.com

Cookies ⌘

• HTTP is stateless
• How does the web application know who the user is?
• Cookies

A simple HTTP request with cookies ⌘

• GET / HTTP/1.1
• Host: www.example.es
• Cookie: Session=ABC12345

HTTP Response codes ⌘

• Many different HTTP response codes
• Most common:

• 200 OK
• 301 Permanent Redirect
• 302 Temporary Redirect
• 404 Not found
• 500 Internal server error
• 503 Bad gateway

Example request/response ⌘

• GET / HTTP1.0
• HTTP/1.0 200 OK
• Content-Type: text/html
• Cache-Control: private
• Content-Type: text/html; charset=UTF-8
• Set-Cookie: SESSION=ABCDEF12345

Try it out ⌘

• telnet www.google.com 80
• GET / HTTP/1.0
• telnet www.google.com 80
• GET / HTTP/1.1
• Host: www.google.es