HTTP (Default Port 80)

HTTP communication consists of a client and a server, where the client requests the server for a resource. The server processes the requests and returns the requested resource. The default port for HTTP communication is port 80, though this can be changed to any other port, depending on the web server configuration. The same requests are utilized when we use the internet to visit different websites. We enter a Fully Qualified Domain Name (FQDN) as a Uniform Resource Locator (URL) to reach the desired website

URL

Resources over HTTP are accessed via a URL, which offers many more specifications than simply specifying a website we want to visit. Let's look at the structure of a URL:

Here is what each component stands for:

Component	Example	Description
`Scheme`	`http://` `https://`	This is used to identify the protocol being accessed by the client, and ends with a colon and a double slash (`://`)
`User Info`	`admin:password@`	This is an optional component that contains the credentials (separated by a colon `:`) used to authenticate to the host, and is separated from the host with an at sign (`@`)
`Host`	`inlanefreight.com`	The host signifies the resource location. This can be a hostname or an IP address
`Port`	`:80`	The `Port` is separated from the `Host` by a colon (`:`). If no port is specified, `http` schemes default to port `80` and `https` default to port `443`
`Path`	`/dashboard.php`	This points to the resource being accessed, which can be a file or a folder. If there is no path specified, the server returns the default index (e.g. `index.html`).
`Query String`	`?login=true`	The query string starts with a question mark (`?`), and consists of a parameter (e.g. `login`) and a value (e.g. `true`). Multiple parameters can be separated by an ampersand (`&`).
`Fragments`	`#status`	Fragments are processed by the browsers on the client-side to locate sections within the primary resource (e.g. a header or section on the page).

Not all components are required to access a resource. The main mandatory fields are the scheme and the host, without which the request would have no resource to request.

HTTP Requests and Response

HTTP communications mainly consist of an HTTP request and an HTTP response. An HTTP request is made by the client (e.g. cURL/browser), and is processed by the server (e.g. web server). The requests contain all of the details we require from the server, including the resource (e.g. URL, path, parameters), any request data, headers or options we specify, and many other options we will discuss throughout this module.

Once the server receives the HTTP request, it processes it and responds by sending the HTTP response, which contains the response code.

Request

The image above shows an HTTP GET request to the URL:

http://inlanefreight.com/users/login.html

The first line of any HTTP request contains three main fields 'separated by spaces':