Basics of Networking
Like never before in history, the world is more interconnected than ever, and this is made possible by a lot of small components working together under the hood to simplify networking tasks such as visiting Nairaland. A lot of what happens when you make a request in your browser to visit a webpage is abstracted away just like everywhere else in the world of computers. I intend to demystify and explain in simpler terms some of the things that happen when you input a target URL into your browser and how you get the right response from the website in response. We will get to see how a web request works and look at the types of different responses the server can send to your Browser.
Networking is one of the major building blocks of the Web as we know it today, but even at that there could be some confusion as to what exactly Networking means. Let’s try and get a clearer picture of the basic concepts of Networking in a way that is easy enough for a beginner to understand. I cannot possibly talk about all aspects of Networking in this post as that is too exhaustive and would require a book, but what i try to do here is to show that none of what happens in a client-server model is magic, although sometimes they are often indistinguishable.
I hope for this post to be a resource for those who may just be curious on what happens behind the scenes and this post can also be used as a reference by Web developers and programmers. Positive feedback and corrections are always appreciated.

So let me begin by asking a rhetorical question; How does the internet even work? And what does it mean to browse the Web? Well it’s very simple, let’s say i needed to visit my nairaland home page, i would just open any browser of my choice and type the following address:
https://www.nairaland.com/playforkeeps which happens to be the specific URL that links to my page on Nairaland’s own website (Servers). And what exactly is a URL anyway? well, it simply means Uniform Resource Location all it does is to provide the address of a specific site or file wanted by the client, in this case its the direct path to my page on nairaland. Its just how resources are identified on the network.
Lets take a look at the components that make a URL what it is and what each part is responsible for.

HTTPS:// Hyper Text Transfer Protocol is an indicator of the type of protocol that the im using to make the request to Nairaland. The HTTP protocol can be found at the Application Layer of the IP protocol suite. WIkipedia says “The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems.” In this case I am using HTTP/2 which uses TLS to make connections more secure than in the previous version of the protocol.
WWW Represents World Wide Web and it indicates the Hostname or the sub-domain.
Nairaland.com This is the domain name of the URL, and it is unique for the Top Level Domain .COM. What this means is that there can’t be two servers with the same domain name in the same TLD, the alternative would be to use .ORG or any other suitable TLD.
.com tld
/playforkeeps This is the path that holds my home page in the Nairaland domain. It's just a subpage.
And that is all that is suitable for a valid URL.
In most enterprise networking environments, you will have a router, and what a router simply does is to connect the local network to the wider internet. Once the router has connected successfully, your query (https://www.nairaland.com/playforkeeps) will be submitted to your ISP (Internet Service Provider e.g. MTN). And the reason I have to allow that is because MTN like all other ISPs has a Domain Name Server (DNS), and what DNS does is to convert the url query (https://www.nairaland.com/playforkeeps/) from the human readable letters to a numerical IP address. The url is converted to an IP because this is the way the Server (Nairaland’s servers) which owns the web page i requested can be found. Once the right Server is found after my request must have hopped from different servers on the internet, my Browser will establish a HTTP connection with the Server and then the Browser sends a HTTP GET request to the server with the specific resource passed along in the GET request. If my account is active, Nairaland will then go ahead and render it in a HTML response to my Browser and then like magic, i am at my home page at which point we can say my request to the Nairaland was successful.
Let's take a look at what a typical Request message looks like for illustration purposes, as a request message can be much more verbose.

Request message:
a request line (e.g., GET /images/logo.png HTTP/1.1)
request header fields (e.g., Accept-Language: en, Content-Type: text/html; charset=UTF-cool
Host (e.g., www.nairaland.com )
an optional message body
The GET verb we used is one of a few others. The HTTP/1.0 specification defined the GET, HEAD and POST methods and the HTTP/1.1 specification added five new methods: OPTIONS, PUT, DELETE, TRACE and CONNECT. All of these methods can be used but only few of them have frequent application. If everything is right in the request message, the server in turn will send a response message to the requesting client and it will have the following components:

a status line which includes the status code and reason message (e.g., HTTP/1.1 200 OK, which indicates that the client's request succeeded)
response header fields (e.g., Content-Type: text/html)
an empty line
an optional message body

This is just a simple introduction to the client-server model workings using the HTTP Protocol. In the response message there will always be a status code which indicates what happened to the request instance, and a code 200 means the HTTP connection to the domain was successful, apart from code 200, there are four other codes. All of the response status codes are as follow:

Informational 1XX
Successful 2XX
Redirection 3XX
Client Error 4XX
Server Error 5XX

Additional Links
https://en.wikipedia.org/wiki/Subdomain
https://en.wikipedia.org/wiki/Hypertext_Transfer_

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