Basics of networking

When we launch a web browser, instant messaging or file-sharing programme, these applications create a communication interface between the computer network and the user. The application software itself, the computer program itself, is not sufficient for efficient communication, as the above communication protocols are required for this, but they are implemented in these programs. An example of an application layer protocol, probably one of the most popular, HTTP, is implemented in web browsers and, like all instant messaging and other programmes that communicate over a network, also implement a corresponding protocol.

When we enter the address of a web page in the browser, the so-called URL (Uniform Resource Locator), and after pressing the Enter key, our browser connects to the server where the page is stored and requests a specific resource - most of which are usually files containing pages of content. If the server has the requested resource, it sends its contents to the browser, which interprets the HTML code of which the page consists, and displays its content to the user. 

The HTTP protocol defaults to port 80 and defines several basic message types, i.e. a request for communication between a client and a web server, the most important of which are: GET and POST.