Hypertext Transfer Protocol (HTTP)

Definition

The Hypertext Transfer Protocol (HTTP) is an application-level protocol used for distributed, collaborative, hypermedia information systems. HTTP is the foundation for data communication on the World Wide Web, establishing a standard way for web browsers and servers to communicate. It operates as a request-response protocol in the client-server computing model.

Detailed Explanation

Client sends an HTTP Request: The process begins when a client (generally a web browser) sends an HTTP request to a target server. This request includes a request line (request method, URL, and HTTP version), headers (additional information about the request or response), and optionally a body (data sent to the server).
Server sends an HTTP Response: When the web server receives the request, it processes it and sends back an HTTP response, which consists of a status line (the HTTP version, status code, and reason phrase), headers, and a body (the requested content or data).

HTTP is stateless, meaning each individual request from a client to a server is treated as an independent transaction, which is separate from any previous request. Because it does not store the state of previous interactions, this makes the protocol both simple and fast.

Examples

GET Request: One of the most common HTTP methods used to request data from a specified resource.
```
1GET /index.html HTTP/1.1
2Host: www.example.com
```

POST Request: This method is used to send data to the server, such as submitting form data or uploading a file.

1POST /submit-form HTTP/1.1
2Host: www.example.com
3Content-Type: application/x-www-form-urlencoded
4Content-Length: 29
5
6field1=value1&field2=value2

Frequently Asked Questions (FAQs)

What are the main HTTP methods?

GET: Requests data from a specified resource.
POST: Submits data to be processed to a specified resource.
PUT: Updates an existing resource or creates a new resource if it doesn’t exist.
DELETE: Deletes a specified resource.
OPTIONS: Describes the communication options for the target resource.
HEAD: Similar to GET, but it transfers only the status line and header section.

Is HTTP secure?

HTTP by itself is not considered secure. Secure communication uses HTTPS (HTTP Secure), which is the secure extension of HTTP. HTTPS uses encryption protocols, such as SSL/TLS, to encrypt data between the client and server.

What is an HTTP status code?

HTTP status codes are issued by a server in response to a client’s request made to the server. They indicate whether the request was successful and inform the client about what action to take next. Common status codes include:

200 OK: The request has succeeded.
404 Not Found: The server can not find the requested resource.
500 Internal Server Error: The server encountered a situation it doesn’t know how to handle.

How does HTTP relate to web development?

HTTP is a fundamental protocol that underpins the World Wide Web, making it essential for web development. Developers use HTTP to deliver web content, interact with APIs, and perform a variety of other Internet-based operations.

HTML (Hypertext Markup Language): The standard markup language used for creating web pages.
HTTPS (HTTP Secure): An extension of HTTP designed for secure communication over a computer network.
URL (Uniform Resource Locator): A reference (an address) to a resource on the Internet.
API (Application Programming Interface): A set of rules that allow different software entities to communicate with each other.

Online References

Suggested Books for Further Studies

“HTTP: The Definitive Guide” by David Gourley and Brian Totty
“Web Protocols and Practice: HTTP/1.1, Networking Protocols, Caching, and Traffic Measurement” by Balachander Krishnamurthy and Jennifer Rexford
“Understanding the Network: A Practical Guide to Internetworking” by Scott Hogg

Fundamentals of Hypertext Transfer Protocol (HTTP): Communications Basics Quiz

### What does HTTP stand for? - [ ] Hyper Textual Transmission Protocol - [ ] Hyperlinked Technology Transfer Process - [x] Hypertext Transfer Protocol - [ ] Hyper Transport Packet > **Explanation:** HTTP stands for Hypertext Transfer Protocol and is used for transmitting hypermedia documents on the internet. ### Which HTTP method is used to request data from a specified resource? - [x] GET - [ ] DELETE - [ ] POST - [ ] PUT > **Explanation:** The GET method is used to request data from a specified resource and is one of the most commonly used HTTP methods. ### What is the key difference between HTTP and HTTPS? - [x] HTTPS uses encryption protocols to secure data. - [ ] HTTPS is slower than HTTP. - [ ] HTTP can only be used for text data, whereas HTTPS can handle all types of data. - [ ] HTTP requires a license fee, HTTPS does not. > **Explanation:** The primary difference between HTTP and HTTPS is that HTTPS uses encryption protocols such as SSL/TLS to secure data during transmission. ### What does a status code "404 Not Found" signify in an HTTP response? - [ ] The server is temporarily unavailable. - [ ] The server has successfully processed the request. - [ ] The resource requires authentication. - [x] The server cannot find the requested resource. > **Explanation:** A status code of "404 Not Found" indicates that the server cannot find the requested resource. ### Which part of the HTTP request message contains the HTTP method? - [ ] Header - [ ] Body - [x] Request Line - [ ] Footer > **Explanation:** The HTTP method is included in the request line of the HTTP request message. ### Is HTTP stateless or stateful? - [ ] Stateful - [x] Stateless - [ ] Both - [ ] Neither > **Explanation:** HTTP is a stateless protocol, meaning that each request from client to server is independent and separate from any previous requests. ### What header field in an HTTP request specifies the internet host and port number of the resource being requested? - [ ] User-Agent - [ ] Content-Type - [x] Host - [ ] Accept > **Explanation:** The "Host" header field specifies the internet host and port number (if any) of the resource being requested. ### In an HTTP request, where can you find additional information about the request or response? - [ ] HTTP Version - [ ] Status Line - [x] Headers - [ ] Protocol > **Explanation:** Additional information about the request or response can be found in the headers section of an HTTP request or response. ### Which organization primarily defines the standards for HTTP? - [ ] Internet Corporation for Assigned Names and Numbers (ICANN) - [ ] World Intellectual Property Organization (WIPO) - [x] World Wide Web Consortium (W3C) - [ ] International Organization for Standardization (ISO) > **Explanation:** The World Wide Web Consortium (W3C) is primarily responsible for defining the standards for HTTP. ### What does a POST request generally carry? - [x] Data to be processed by the server - [ ] URL redirection commands - [ ] Web page meta information - [ ] Uniform Resource Identifiers (URI) > **Explanation:** A POST request generally carries data to be processed by the server, such as form submissions or file uploads.

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