HTTP, or HyperText Transfer Protocol, is a fundamental protocol used for transmitting hypermedia documents, such as HTML pages, over the internet. It operates as a request-response protocol in a client-server model. Clients, typically web browsers, initiate requests to servers to retrieve resources like web pages or data. Servers respond to these requests by providing the requested resources or indicating an error if the resource cannot be found. HTTP works over TCP/IP, with communications occurring over port 80 for standard HTTP and port 443 for HTTPS (HTTP over SSL/TLS).
The working process of HTTP involves several key steps:
- Request: A client sends an HTTP request to a server. The request includes a method (such as GET, POST, PUT, DELETE) that specifies the action to be performed, a URL identifying the resource, and optional headers providing additional information like content type or authentication credentials.
- Routing: Upon receiving the request, intermediary devices like routers direct it to the appropriate server based on the destination URL.
- Processing: The server processes the request by interpreting the HTTP method, headers, and optional message body (for methods like POST or PUT). It retrieves the requested resource or performs the requested action.
- Response: The server generates an HTTP response that includes a status code (indicating the success or failure of the request), response headers providing metadata about the response (such as content type and cache control), and an optional response body containing the requested resource or error message.
- Delivery: The server sends the HTTP response back to the client over the established TCP connection.
- Rendering: The client receives the response, interprets the data based on the content type (e.g., HTML, JSON), and renders it for the user to view or interact with.
Basic HTTP works by establishing a connection between a client and a server, sending a request for a specific resource, and receiving a response containing the requested resource or indicating an error. It is a stateless protocol, meaning each request-response cycle is independent and does not retain information about past interactions. This simplicity makes HTTP suitable for a wide range of applications, from retrieving web pages to exchanging data between clients and servers.
HTTP methods define the actions that clients can perform on resources identified by URLs. The primary HTTP methods include:
- GET: Retrieves data from a specified resource.
- POST: Submits data to be processed to a specified resource.
- PUT: Updates a resource or creates a new resource if it does not exist.
- DELETE: Deletes a specified resource.
- HEAD: Retrieves headers identical to those of the GET method, without the response body.
- OPTIONS: Describes the communication options for the target resource.
- PATCH: Applies partial modifications to a resource.
Each method has specific semantics and usage scenarios, enabling clients to interact with servers in different ways based on the desired action. For example, GET is used for retrieving data, POST for submitting data, PUT for updating or creating resources, and DELETE for removing resources from the server.
HTTP GET is a method used by clients to request data from a server. When a client sends an HTTP GET request, it typically includes a URL specifying the resource it wants to retrieve. The server processes the request and responds with the requested resource, such as an HTML document, image, or other types of data. GET requests are considered “safe” and “idempotent,” meaning they should not modify server state and can be repeated without causing different outcomes. This method is commonly used for fetching web pages, images, and other static content from web servers.