Understanding HTTP: Client, Server, IP Address, Domain Name

 
Client, Server, HTTP, IP Address, Domain Name
 
Client-Server Model
Client 
Bob
Yahoo Server
 
http://
yahoo.com/finance.html
 
A text file named
finance.html
 
Internet
 
HTTP: Hypertext Transport Protocol
 
HTTP is a form of communication protocol which
specifies how web clients and servers should
communicate.
 
The basic structure of HTTP follows a 
request-response
model.
 
A client always 
initiates
 a request message to the server;
the server generates a response message.
 
HTTP Request Message
 
Every HTTP request message has the same basic
structure:
Start Line (request method, URI, HTTP version)
Header field(s) (one or more)
Blank line
Message body (optional)
 
GET /tian/public_html/teaching.html HTTP/1.1
    host: ww2.cs.fsu.edu
 
HTTP Request Method
 
GET: request server to return the resource specified by
the Request-URI as the body of a response message
 
 
POST: pass the body of this request message on as data
to be processed by the resource specified by the
Request-URL
 
HTTP Header Fields
 
The Host header field is required in every HTTP/1.1
request message.
 
Three major header fileds:
Host: 
www.yahoo.com
User-agent: Mozilla/5.0 (Windows)
Accept: text/html, application/xml (MIME types)
Content types that are acceptable  for the response
 
HTTP Response Message
 
Every HTTP response message has the same basic
structure:
Status Line (HTTP version, status code, Reason Phrase)
Header field(s) (one or more)
Blank line
Message body (optional)
 
HTTP/1.1 200 OK
    HTTP/1.1 404 NOT FOUND
 
Example of HTTP Request Message
 
Try to retrieve the file at
http://ww2.cs.fsu.edu/~tian/public_html/webDevelopme
nt.html
 
GET /~tian/public_html/webDevelopment.html HTTP/1.1
Host: ww2.cs.fsu.edu
User-Agent: Molliza9.0 (Windows)
Accept: text/html
 
Example of HTTP Response Message
 
HTTP/1.1
Date: Fri, 31 Dec 1999 14:20:00 GMT
Content-Type: text/html
Content-Length: 1354
 
<html>
     <body>
  <p>Welcome to CGS 3066</p>
</body>
</html>
 
IP address and Domain Name
 
Every computer on the Internet has an IP address such as
192.0.34.166
 
Humans find it easier to refer to computers by names,
such as 
yahoo.com
. This is called host/domain name.
 
DNS (Domain Name Service) provides a mechanism for
mapping back and forth between IP addresses and host
names.
Client-Server Communication
Client 
Bob
DNS
 
What is the IP address of
yahoo.com
 
yahoo.com’s IP
address is
98.138.252.30
Yahoo
Server
 
HTTP Request
 
HTTP Response
 
Web Client
 
Web client is a software that accesses a web server by
sending an HTTP request message and processing the
resulting HTTP response.
 
Web Browser is a typical web client.
IE, Firefox, Safari, etc
 
Browser-Wars
En.wikipedia.org/wiki/Browser_wars
Each company trying to add features and performance to its
browser in order to increase its market share.
 
Browser War
 
What are the advantages?
 
What are the disadvantages?
 
 
Despite this diversity, all of the major modern browsers
support a common set of basic user features and provide
similar support for HTTP communication.
 
Server
 
The primary feature of every web server is to accept
HTTP request from web client and return an
appropriate resource (if available) in the HTTP
response.
 
1. Wait for connection requests from a client.
2. Receive an HTTP request.
3. Finding the requested file and creates an HTTP response
that contains the file in the body of the response message.
 
Next Class
 
History of HTML
Basic elements of HTML5
Write your first web page in HTML5
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HTTP, or Hypertext Transfer Protocol, is a vital communication protocol that governs how web clients and servers interact. It entails a structured request-response model where a client initiates a request to a server, which generates a response. Key components include client-server interactions, IP addresses, domain names, HTTP methods, header fields, and response messages.


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  1. Client, Server, HTTP, IP Address, Domain Name

  2. Client-Server Model A text file named finance.html Yahoo Server Internet Client Bob http://yahoo.com/finance.html

  3. HTTP: Hypertext Transport Protocol HTTP is a form of communication protocol which specifies how web clients and servers should communicate. The basic structure of HTTP follows a request-response model. A client always initiates a request message to the server; the server generates a response message.

  4. HTTP Request Message Every HTTP request message has the same basic structure: Start Line (request method, URI, HTTP version) Header field(s) (one or more) Blank line Message body (optional) GET /tian/public_html/teaching.html HTTP/1.1 host: ww2.cs.fsu.edu

  5. HTTP Request Method GET: request server to return the resource specified by the Request-URI as the body of a response message POST: pass the body of this request message on as data to be processed by the resource specified by the Request-URL

  6. HTTP Header Fields The Host header field is required in every HTTP/1.1 request message. Three major header fileds: Host: www.yahoo.com User-agent: Mozilla/5.0 (Windows) Accept: text/html, application/xml (MIME types) Content types that are acceptable for the response

  7. HTTP Response Message Every HTTP response message has the same basic structure: Status Line (HTTP version, status code, Reason Phrase) Header field(s) (one or more) Blank line Message body (optional) HTTP/1.1 200 OK HTTP/1.1 404 NOT FOUND

  8. Example of HTTP Request Message Try to retrieve the file at http://ww2.cs.fsu.edu/~tian/public_html/webDevelopme nt.html GET /~tian/public_html/webDevelopment.html HTTP/1.1 Host: ww2.cs.fsu.edu User-Agent: Molliza9.0 (Windows) Accept: text/html

  9. Example of HTTP Response Message HTTP/1.1 Date: Fri, 31 Dec 1999 14:20:00 GMT Content-Type: text/html Content-Length: 1354 <html> <body> <p>Welcome to CGS 3066</p> </body> </html>

  10. IP address and Domain Name Every computer on the Internet has an IP address such as 192.0.34.166 Humans find it easier to refer to computers by names, such as yahoo.com. This is called host/domain name. DNS (Domain Name Service) provides a mechanism for mapping back and forth between IP addresses and host names.

  11. Client-Server Communication What is the IP address of yahoo.com DNS Client Bob yahoo.com s IP address is 98.138.252.30 HTTP Request HTTP Response Yahoo Server

  12. Web Client Web client is a software that accesses a web server by sending an HTTP request message and processing the resulting HTTP response. Web Browser is a typical web client. IE, Firefox, Safari, etc Browser-Wars En.wikipedia.org/wiki/Browser_wars Each company trying to add features and performance to its browser in order to increase its market share.

  13. Browser War What are the advantages? What are the disadvantages? Despite this diversity, all of the major modern browsers support a common set of basic user features and provide similar support for HTTP communication.

  14. Server The primary feature of every web server is to accept HTTP request from web client and return an appropriate resource (if available) in the HTTP response. 1. Wait for connection requests from a client. 2. Receive an HTTP request. 3. Finding the requested file and creates an HTTP response that contains the file in the body of the response message.

  15. Next Class History of HTML Basic elements of HTML5 Write your first web page in HTML5

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