HTTP

Question 1

What is HTTP and what is its use?

Answer 1

Hypertext Transfer Protocol
- Describes how a program called the client can send a request (e.g., retrieve a document) to
- Another program called the server which sends back a response (e.g., containing the requested document) back to the client

Question 2

What is a URL and what is its use

Answer 2

Uniform Resource Locator (URL) is a type of URI (Uniform Resource Identifier).
- Identifies the location of a resource
- Contains some required and some optional parts
- A naming infrastructure to represent documents, or more formally resources, located on the web. We commonly call a URL a web address.

• Typically the client and server programs run on different machines. In such cases, the url identifies both the machine on which the server is running as well as the specific document among all the other documents hosted by that server. The URL naming infrastructure thus allows retrieval of documents that are located across geographically distant places, i.e., across a wide area.

scheme://server-name:port-number/path-to-resource?param1=value1&param2=value2#link-in-resource

Question 3

What is HTML and what is its use

Answer 3

Hypertext Markup Language - A markup language for describing documents that can be retrieved over the web.
- The term hypertext means text which contains links to other texts
HTML supports describing hypermedia documents, i.e., documents that besides text, can also contain other media such as graphics, video, and sound
- A client interprets the HTML in a document it receives in the HTTP response from the server and displays the document.

Question 4

What is Javascript and what is its use?

Answer 4

A programming language which can be executed by web browsers, and is also used as a general purpose programming language. It is also very popular for implementing server side programs.
- it was developed in order to allow running programs in the browser to support full-blown applications with rich user interfaces and good performance that did not require round-trip communication to the server for every user interaction.

Question 5

What is CSS and what is its use?

Answer 5

Developed as a way to provide developers a way to have more control over the look and feel of their webpages. Also allows for displaying webpages differently based on screen differences.
- Allows for separating the styling aspects of a webpage, e.g., colors, fonts, etc., from its structure.
- Used for describing the presentation of documents on the web while HTML continues to be used for describing the structure of documents.

Question 6

What is a server

Answer 6

A server receives the HTTP request from a client and determines the document that has been requested.

Question 7

What is a client

Answer 7

A client is a web browser.
A client on the web communicates with the server using HTTP protocol.

Question 8

How do a client and a server communicate over the web

Answer 8

A user enters a URL in the browser (client)
- The browser sends an HTTP request to the appropriate web server as identified by the URL
- The server receives the HTTP request and determines the document that has been requested
- The server sends back the document in an HTTP response to the browser
- The browser interprets the HTML document and displays its contents.

Question 9

What are the different parts of an HTTP request

Answer 9

An HTTP request has up to 4 parts.
1. The request line, the first line which has the following format: Request-Method Resource HTTP/Version
2. Request Headers: these take the form of a name:value pair
3. A blank line
4. An optional body, usually empty for a Get request, but contains the content in a POST request

Question 10

What is in a request line?

Answer 10

Request-Method Resource HTTP/Version

Question 11

What is the GET method used for?

Answer 11

The GET method is used to retrieve a document

Question 12

What is the use of request headers?

Answer 12

Used to pass additional information to the server.

Question 13

What re the different parts of an HTTP response

Answer 13

Status Line
Response Headers
Blank Line
Optional Body

Question 14

What is in the status line?

Answer 14

HTTP/Version Status-code Reason-phrase

Question 15

What is the use of response code?

Answer 15

This code provides the status of the response.
200 - successful request
400 - the request failed because of a client error
500 - the request failed because of a server error

Question 16

What is the use of response headers?

Answer 16

These take the form of name:value pairs
Almost all responses contain at least a Date and Content-Type header
- The content-type header tells the browser the format of the resource sent in the body of the response
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Question 17

What may be contained in a response body?

Answer 17

Contains the resource.

Question 18

What is a scheme?

Answer 18

This identifies the protocol used to send the request. HTTP, HTTPS

Question 19

What are the server name and port?

Answer 19

The name of the machine where the resource is hosted and to which the request must be sent

The endpoint to which data is routed.

Question 20

How does a URL specify which resource it wants from the server?

Answer 20

The path to the resource is included in the url as the fourth parameter

Question 21

What is the use of query parameters?

Answer 21

These are optional key-value pairs separated by & and they are used to provide additional information to the program to be executed for processing the request