First of all, what is a protocol? A protocol is a set of rules used by computers to communicate. A protocol may include signals, authentication methods and possibilities of detection and correction of errors. A protocol describes the syntax, semantics, and synchronization of messages. As a broader definition, we can say that a protocol is used as a set of procedures (or rules) used to communicate.
HTTP means HyperText Transfer Protocol. It is the protocol used throughout the 'World Wide Web' and it is a cornerstone in its use. HTTP is a protocol used in request-response client-server model. Thus, a customer (eg a browser) sends an HTTP request to server. The server is used to store data, and resources (for example, a Web page or an image are considered resources) but also other functions for the client, returns a message to the Client.
The answer provided by the server contains information about completing the application and can contain any content requested by clients. A client may be not only a Web browser. Let's think, for example, of web-crawlers that search engines use to crawl the web. HTTP protocol is used mainly on the structure of another protocol, TCP / IP. TCP / IP is the protocol used to actually transfer from client to server.
HTTP resources are recognized by an identifier in the network, or URI (Uniform Resource Identifiers), or specific URL (Uniform Resource Locator). HTTPS (HyperText Transfer Protocol Secure) is used to send encrypted information between the client and the server. It uses, like the HTTP protocol, TCP / IP, but, instead, uses another encryption protocol, that is called SSL / TLS. This protocol uses symmetric cryptography, security, and a message authentication key. So, we learned what's HTTP and what it is used for - for accessing files on other computers, remote from our own computer.
Let's talk a bit about HTTP session. A session is a sequence of HTTP Request-Response transactions. An HTTP client initiates a request. It makes a TCP connection on a particular port on the server (usually 80 for a web server). An HTTP server is listening on that port for a customer's request. After it receives the request, the server sends the client a status line (for example, "HTTP/1.1 200 OK") message or a resource or an error message or any other information.
Request message consists of the following:
- A line of request, such as GET / images / logo.png HTTP/1.1, which will require, for example, a image named logo.png that is located in the images folder on the server.
- Headers, such as Accept-Language: en
- An empty line
- A message content, which may be empty
The request line and the headers must end with (carriage return followed by a line feed), which should not contain any empty space. Request lines. Overall, the HTTP site was created to support nine methods (verbs, really) meant to suggest the action that will be executed for the resource identified.
The nine methods used are: HEAD, GET, POST, PUT, DELETE, TRACE, OPTIONS, CONNECT PATCH. For more information, you can use Google here.
To be continued.
Cosmin | Pixelfind
