The Hypertext Transfer Protocol (HTTP) is the application layer protocol that uses messages.
HTTP: The Message-Based Protocol
HTTP is fundamental to how web browsers communicate with web servers. It uses a request-response model, sending messages back and forth to retrieve web resources. These messages come in specific formats and carry important information.
Types of HTTP Messages
HTTP utilizes various message types, each serving a different purpose:
- GET: This message requests data from a specified resource. For example, a browser sends a GET message to get the HTML content of a webpage.
- POST: This message sends data to a server to create or update a resource. For instance, a user submitting a form would use a POST message.
- PUT: Similar to POST, but designed for updating a resource at a specific URL.
- DELETE: This message requests the deletion of the specified resource.
- HEAD: This message is like GET, but it only requests the headers, not the body of the response. This is useful for checking if a resource has been modified.
- OPTIONS: This message is used to find out the available communication options associated with a resource.
- CONNECT: Used for establishing a network connection to a server over a proxy.
- TRACE: This message is used to perform a diagnostic loop back of the message to the client, useful for troubleshooting.
- PATCH: Used for modifying a resource, but, unlike PUT, it modifies parts of the resource rather than replacing the whole thing.
How HTTP Messages Work
HTTP messages consist of:
- A Request Line/Status Line: Which defines the method/status, resource, and version
- Header Fields: Provide additional information such as encoding, caching options, or authentication
- A Body (Optional): Containing the actual data, like HTML content or form data
This structure ensures that both the client and the server can understand the messages being exchanged, enabling seamless communication across the web. The reference highlights that HTTP uses message types like GET, PUT, and POST which are indeed a part of the message structure.
| Message Type | Function |
|---|---|
| GET | Requests data from a resource |
| POST | Sends data to create or update a resource |
| PUT | Updates a resource at a specified URL |
| DELETE | Requests the deletion of a resource |
| HEAD | Retrieves the headers of a resource |
| OPTIONS | Checks the available communication options for a resource |
| CONNECT | Establishes a network connection through a proxy |
| TRACE | Performs a loopback test for debugging |
| PATCH | Modifies a resource partially |
