The objective of this chapter is to discover the fundamental concepts related to Web development.
The functioning of the Houston web design
To view a website on the Internet, simply type the correct site address in the address bar of a web browser, and the site will be displayed (if network access is working). We will try to understand what is behind this very simple operation in appearance.
The concept of Web server
To be accessible, a website must be published on a server. A server is a particular type of computer whose role is to wait for and respond to client requests. A server renders a service to its customers.
There are many types of servers, depending on the service rendered: file server, mail, authentication … A server that publishes websites is called a Web server.
Note: the same machine can render different services (example: Web server and file server).
Specifically, a web server machine embeds and executes server software capable of responding to requests for web site queries. The most popular web server software is Apache, Microsoft IIS and nix.
Read more- Houston web design
The notion of Web client
The machine that allows consultation of the requested website is called Web Client. This is an abuse of language: in reality, the real client is software that runs on this machine and performs the consultation operation. This software is most often a Houston web design browser (browser). The most popular web browsers are Internet Explorer , Mozilla Firefox , Chrome , Safari and Opera .
Other types of software than browsers can act as web clients by connecting to web servers. Examples: indexing robots, web vacuums, mobile applications, etc.
Communication between client and server
The understanding of the exchanges taking place between a client and a Web server during the consultation of a site is essential. This is a request / response mechanism.
The exchange is initiated by the client, which sends the server a request to consult a web resource.
The server prepares the associated HTML page.
The server returns the HTML page to the client, who displays it.
In order to understand each other, the client and the web server use a common protocol during their exchanges: HTTP.
The HTTP protocol
HTTP (Hypertext Transfer Protocol ) is the transfer protocol of the Web. It was his invention in 1989 at CERN in Geneva, along with HTML, that led to the appearance of the World Wide Web: an immense network of networks, where we can “bounce” from a Web page to another using links without having to know the physical location of the servers and resources consulted.
HTTP is basically a very simple protocol, based on textual commands.
The first line of this HTTP request is the most important. It contains:
The method associated with the query: here, GET means a resource request.
The identifier of the resource concerned. Here, /(root symbol, as in Linux) indicates that you want to access the default document.
The version of the HTTP protocol, here 1.1.
The other lines of the HTTP request are called header fields ( HTTP header fields or more simply headers ). They specify the website concerned (field Host), the types of content accepted by the client (field Accept) and the client software used (field User-Agent). There are other header fields, not shown here.
The most frequently used HTTP methods are GET(to retrieve a resource from the server) and POST(to modify a resource on the server). There are others like HEAD, PUT or DELETE.
Anatomy of an HTTP response
When it receives an HTTP request, the Houston web design server pulls in the information needed to build the response, and sends it back to the client. Let’s continue with our previous example
The first line of the response contains its status in the form of a code that indicates the result of the request. Like a request, an HTTP response contains header fields ( Date, Content-Type and many others) for conveying additional information. For example, it is possible to use certain fields to set up a cache mechanism.
Finally, the HTTP response optionally contains the resource requested by the client. Most often, it is a web page described as HTML tags.