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Web Technologies-I

Notes The body of the message is either the content being sent from the server to the client, or form
data or an uploaded file being sent from the client to the server. In other words, it is the thing
we think of as being the document we sent or received. Not much more needs to be said about
that here. However, the other two sections can use some explanation.
The Hypertext Transfer Protocol (HTTP) is a networking protocol for
distributed, collaborative, hypermedia information systems; HTTP is the
foundation of data communication for the World Wide Web.

9.1.1 Request and Response
If the request line can be seen as a specification of what to order from whom, the response line
can be seen as the receipt confirming that the transaction took place. There can only be one of
the two in any message.
The request contains three critical pieces of information. The first is the method of request, which
is to say, how the server is supposed to process it. The second is the path to the resource being
requested. The third is the version number of HTTP being used.

The method tells the server how to handle the request. The three most common are GET, HEAD,
and POST.
GET
This is a simple request for a document or resource residing at a specific URI (Uniform Resource
Indicator). It is the most common type of Web request.
HEAD
This is similar to a GET request, except that it is only looking for HTTP header information on
the resource, not the resource itself.
POST
Indicates that information is being sent the server inside the HTTP body. The URI should point
to a resource capable of handling the data being posted.
A typical request header might look something like this:
GET /index.php HTTP/1.1
The reply line indicates whether the request was successful. It includes the protocol being used,
a numeric status code, and a short description of the status code.
HTTP/1.1 200 OK
The numeric status codes fall into the following ranges:
100-199
Information messages on the current status of processing.
200-299
Successful request.

300-399
Request cancelled because document or resource has been moved.
400-499
Client error. The request was incomplete, incorrect, or otherwise unresolvable.
500-599
Server error. Request appears valid, but server could not complete it.

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