HTTP stands as the fundamental protocol for data communication on the World Wide Web. It operates on a strict client-server paradigm, where a client (most commonly a web browser) initiates a request, and a server (a web server) provides a response. HTTP primarily relies on the Transmission Control Protocol (TCP) for reliable, ordered, and error-checked data transfer, typically communicating over port 80 for unencrypted traffic and port 443 for encrypted connections secured by TLS/SSL (HTTPS).

HTTP communication is characterized by the exchange of distinct request and response messages, both adhering to a similar structural layout.

HTTP Request Message (Client to Server):

• Request Line: This is the first line of the message, containing three essential elements:
• Method: An uppercase verb indicating the desired action to be performed on the identified resource (e.g., GET, POST, HEAD, PUT, DELETE).
• URL: The complete path or address of the resource being requested (e.g., /index.html, /api/users/123).
• HTTP Version: The version of the HTTP protocol being used by the client (e.g., HTTP/1.1, HTTP/2.0).
• Header Lines: Provide additional information about the request, such as the client software making the request, and media types the client can process.
• Entity Body (Optional): This section contains data being sent to the server, typically used with methods like POST.

HTTP defines a set of standard methods (verbs) to specify the action to be performed on the identified resource.
- GET: Used to request data from a specified resource. It is idempotent and safe.
- POST: Used to submit data to a specified resource and is not idempotent.
- HEAD: Similar to GET but requests only the response headers.
- PUT: Used to upload or update a resource.
- DELETE: Used to remove the specified resource from the server.

These three-digit integer codes, accompanied by a brief reason phrase, provide a quick summary of the server's response to an HTTP request.
- 1xx (Informational): The request was received and is continuing.
- 2xx (Success): The request was successful.
- 200 OK: Standard success response.
- 3xx (Redirection): Further action needs to be taken by the client.
- 301 Moved Permanently: Resource has been moved.
- 4xx (Client Error): There was an error with the request.
- 404 Not Found: Resource could not be found.
- 5xx (Server Error): The server encountered an error.

HTTP is inherently a stateless protocol, meaning that each request-response pair is treated independently. However, cookies are a mechanism to introduce state into the otherwise stateless HTTP. They are small pieces of data that a website sends to a user's web browser.
- Set-Cookie Header: Used to set cookies in HTTP responses.
- Cookie Management: Browsers store cookies and send them back with requests.

SMTP is the foundational application-layer protocol for transmitting email messages across the internet. It operates as a 'push' protocol, meaning the sending mail server initiates the connection and actively pushes the email message to the receiving mail server. SMTP primarily uses TCP port 25 for communication between mail servers.

SNMP is an application-layer protocol designed for managing and monitoring network devices. It empowers network administrators to remotely collect operational information, modify device configurations, and receive event notifications from a wide array of network devices. SNMP primarily uses UDP port 161 for agent listening and port 162 for manager traps.

Web applications represent the dominant paradigm for delivering software services in the contemporary internet landscape. They are software applications that reside and execute on a web server, accessed by end-users via a standard web browser over a network connection.