HTTP/HTTPS

HTTP (Hypertext Transfer Protocol) is a standard protocol that is mainly used for IP communication between servers and clients on the Internet. The client is usually a web browser that requests a website from a web server. Another use case for the HTTP protocol is REST (Representational State Transfer) web services.

Furthermore, HTTP is a stateless protocol, each command is handled independently. After a server has responded to a client request, the connection is closed again. A client has the option of informing the server that the connection should be maintained after a request.

HTTP methods

The HTTP standard (version 1.1) defines different methods that a HTTP server can offer to requesting clients. In particular, GET, POST, and PUT are some of the most commonly used HTTP methods. The following table contains all HTTP methods defined in the standard.

HTTP method	Description
GET	Requests a resource from the server.
POST	Transfers data to the server.
PUT	Replaces or creates a resource on the server with the request payload.
CONNECT	Establishes a SSL tunnel to a server.
DELETE	Deletes the addressed resource from the server.
HEAD	Same functionality as GET, without payload data.
OPTIONS	Requests the available communication options from the server.
TRACE	Performs a message loopback for testing purposes.
PATCH	Same functionality as PUT, but used for partial changes of resources.

A user must know that not every server implements all these methods. According to the specification, only GET and HEAD are mandatory for a specification-compliant server, all other commands are optional. There is also the possibility that user credentials are required to access resources on a server.

HTTP status codes

An HTTP response is divided into header and body. An important part of this response is the HTTP status code. The HTTP status code delivers information about the request back to the client. The following table shows the defined ranges of the HTTP status code.

Status code range	Description
100-199	Status codes that contain information messages.
200-299	Status codes that inform the client about a successful request.
300-399	Status codes that show a diversion and request an interaction from the user.
400-499	Status codes that show error messages (triggered by the client).
500-599	Status codes that show error messages (triggered by the server).

HTTPS

HTTPS (Hypertext Transfer Protocol Secure) is an extension of the HTTP protocol, which implements TLS (Transport Layer Security). Data sent using the HTTP protocol is completely unencrypted and therefore does not meet the security requirements for sending passwords or credit card information, for example. In addition to the encryption of transported data, HTTPS also offers server authentication.