2. Definition
● An application protocol used to
communicate/deliver data on The WWW.
● The protocol to ‘transfer’ hypertexts.
● Stateless request/response protocol.
● Exchanges messages over a session layer or
a connection.
● Uses port 80,8008, and 8080.
3. HTTP Roles
● HTTP Client: A program that establishes a connection
with a server for the purpose of sending an HTTP
request.
● HTTP Server: A program that accepts a connection to
provide service for the HTTP request by sending HTTP
response.
● The same program can either be a client or a server,
depending on what is it doing.
4. HTTP Exchange/Transaction
A HTTP client establishes a connection with a
HTTP server and sends the server HTTP
request, the server returns HTTP response.
When the response is received, the connection
is terminated.
5. Request/Response Message Format
● Initial line ( request/response)
● header line ( or none)
● blank line -> to indicate the ending of
header section
● message body ( data payload), optional
section.
6. Initial Line | HTTP Request Format
HTTP request has 3 sections separated by a space.
● HTTP method name
● URL host path
● HTTP protocol version
GET /path/to/file/index.html HTTP/1.1
Note: HTTP protocol always takes this format
HTTP/ x.x
7. Initial line | Response Message Format
Response message or status message also takes three
parts separated by a space.
● HTTP protocol version
● status code
● textual status code
HTTP/1.1 200 OK
8. Status Code
status code is a 3 digit number, the first digit
indicate the category of the code
1xx - indicates information message
2xx- indicates success
3xx- redirect client to another URL
4xx- error on the client side
5xx- error on the server side
9. HTTP Methods/Functions
● A HTTP method name is always uppercase.
● The most common HTTP methods are: GET,
HEAD, POST and PUT.
10. GET METHOD
This method GETS the web page or generally,
the requested resource.
GET /path/to/file/index.html HTTP/1.1
11. HEAD Method
The same as the GET method, but it asks the server to
return the response header not the resource data.
There is no message body, just status line and the
headers.
It is useful if you want to know information about the file,
or the the resource without downloading it.
HEAD /hello.htm HTTP/1.0
12. POST Method
This method sends/submits data to the server in some
way to update it.
What is the difference between a GET and a POST?
● The data in a post is sent with the request, in the
message body such as the content type or content
length.
● The resource URI is not something you download, it is
a program to handle the data you’re sending.
● The response is a program output, not a static file.
14. PUT Method
PUT requests the server to put/store the included
message body in the given URL.
PUT /hello.htm HTTP/1.0
headrName:..
..
<html> <body> <h1> Hello World!
</h1></body></html>
16. CONNECT Method
The client uses this method to establish a
network connection to a web server over
HTTP.
CONNECT www.testWebsite.com HTTP/1.0
17. OPTIONS Method
it is used by the client to investigate the
methods and the options that are run by the
server. The client can either use a URL or * in
the request method.
OPTIONS /someURL HTTP/1.0
OPTIONS * HTTP/1.0
18. TRACE Method
Used to trace the contents of HTTP request.
Used for debugging.
TRACE HTTP/1.0
