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Day 1

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Day 2

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Day 3

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Day 4

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Day 5

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Day 6

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🌐 Introduciton to Internet

Imagine you have top-secret cat memes on your computer (Computer A) 🐱💻 and you desperately want to send them to your friend’s computer (Computer B) 🖥️—but alas, they’re not sitting next to you! The old-school way?

Carry a USB stick like a tiny digital courier 🏃‍♂️💨. Works, but slow… and not great if you have 1,000 memes.

So instead, we invent magic internet cables ✨—aka ethernet or fiber optic lines. Now we can send messages as tiny flashes of light or electricity ⚡💡. High voltage = “1,” low voltage = “0.” It’s like Morse code for computers! Boom! 🎉 We just created the first-ever network: a direct link. Your memes can now travel between computers without you running around like a caffeinated hamster 🐹.

Here we have Preethi and Kabir—two computers sitting in their digital world. Preethi wants to say “Hi!” 👋 to Kabir, but computers are picky about addresses. You can’t just shout across the internet like a human.

So Preethi writes down Kabir’s IP address (192.68.3.2) ✍️📬 and sends the “Hi!” message. Kabir sees it, smiles 😎, and replies with “Preethi!!”, but it needs to know where to send it back. Luckily, Preethi’s IP (192.68.2.111) is written clearly on the envelope.

Think of it like digital pen pals:

Now What is this "192.68.3.2" Even Mean Why do i need it to talk to my PREETHI!

Think of it like digital pen pals:

Each computer has a home address (IP) 🏠.

Messages hop across invisible wires or Wi-Fi magic ✨.

Without addresses, your “Hi” could get lost forever in the internet void 🌌.

So basically, the image is a cute digital conversation where two computers are being polite, sending “Hi!” and “Preethi!!” back and forth using their unique addresses, like proper internet citizens 👩‍💻👨‍💻. Basically think of it as an address (it is a address)

An  IPv4 (Internet Protocol version 4)** address is the classic IP address format everyone is used to seeing.

Structure: It's a 32-bit number. To make it readable for humans, we divide it into four 8-bit sections, and write each section as a decimal number from 0 to 255.

- Example: 172.217.16.142 (one of Google's addresses)

The Big Problem (The Why): A 32-bit number means there's a hard limit on the total number of possible addresses: 2^32, which is about **4.3 billion**.

When the internet was designed, 4.3 billion seemed like an infinite number. But with the explosion of laptops, phones, servers, smart watches, and even smart refrigerators, we quickly realized we would run out. This scarcity is the **single most important reason** we have public and private IPs.

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But who gave Preethi & Kabir This "IP Address? 🤔

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An IP address is your device’s unique “house number” on the internet. 🏠 ISPs like Airtel, Jio, BSNL, ACT give these numbers so that Preethi and Kabir can talk to each other using there computer. 📬

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DNS(Domain name space)

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Preethi wants to visit a website called www.coolmemes.com .

But her computer, only understands numbers, not names. 😅



Enter DNS (Domain Name System) — think of it as the internet’s phonebook or a super smart friend:



Preethi: “I want to go to www.coolmemes.com!”

DNS: “Ah! That’s 192.168.1.5. Computer, take her there!” 🚀



So DNS is basically a translator between human-friendly names and computer-friendly numbers. Without DNS, Preethi would have to memorize websites like 192.168.1.5, and nobody wants that 😜

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Public IP & Private IP

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🌍 Public IP Address

What it is: Your global, unique internet address.


Analogy: Like a company’s main phone number—anyone in the world can dial it. 📞

Uniqueness: Must be one of a kind worldwide.
Who gives it: Your ISP (Airtel, Jio, Comcast). You borrow it from them.

Who uses it: Routers, servers (Google, Netflix).

Fun fact: When you check whatismyip.com, it shows your router’s public IP. From outside, your whole home looks like one device. 🏠

🏡 Private IP Address


What it is: A local address inside your home/office network.

Analogy: Like an employee’s 4-digit extension number—works only inside the office. ☎️

Uniqueness: Must be unique only inside your local network, not globally.

Who gives it: Your router automatically assigns it.
Keeps changing: These are often dynamic—every time your phone reconnects to Wi-Fi, your router may give it a new private IP. 🔄
Purpose: Lets your devices talk locally (laptop → printer, phone → TV).
Reserved ranges:
10.x.x.x (big companies)
172.16.x.x – 172.31.x.x (medium networks)
192.168.x.x (most home Wi-Fi)

👉 In short:
Public IP = Your house’s main address on the internet 🌍 (global, fixed for a while).
Private IP = The room numbers inside your house 🏡 (local, often keeps changing).

IPv6 & IPv4

📦 IPv4(Internet Protocol version 4)
Format: 32-bit address → looks like 192.168.1.1
Total addresses: About 4.3 billion (seemed huge in the 80s, but now… too small for today’s internet).
Analogy: Like giving out phone numbers with only 10 digits—eventually, you run out. 📞
Fun fact: Most of today’s internet still runs on IPv4.

🚀 IPv6 (Internet Protocol version 6)
Format: 128-bit address → looks like 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Total addresses: A mind-blowing 340 undecillion (that’s 340 trillion trillion trillion!) 🌌 Enough for every grain of sand on Earth to have millions of IPs.
Analogy: Like switching to phone numbers with infinite digits—no running out, ever.
Fun fact: IPv6 also has built-in security and efficiency improvements.

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Mac Address & Port number

Imagine Preethi wants to send a funny meme to Kabir over the internet. Sending data isn’t as simple as just knowing his house! Here’s what happens:


IP address → The house number. Tells the internet which computer to send the data to. 🏠

Port number → The room inside the house. Kabir’s computer might have a browser (room 80) or an email client (room 25). The port tells the data exactly where to go. 🛋️📧

MAC address → The mailbox ID. Even if multiple computers are in the same building (local network), this unique hardware ID ensures the package reaches the correct computer. 📬

Protocol → The delivery rules. TCP makes sure every meme piece arrives safely and in order, while UDP just throws it over quickly, like express delivery. 🚚⚡

So sending data is like:

“Kabir, here’s a meme for your browser (port 80) at your house (IP 192.168.1.5). Use your mailbox (MAC) and follow the delivery rules (TCP)!” 😹

Without any one of these, your data could get lost, end up in the wrong program, or arrive as gibberish.

All This is required to share date from one end to another end

LAN (Local Area Network)

Inside the LAN (Local Area Network), all the friends — Preethi, Simran, Sumukhi, Kabir, and Jack — live in the same “apartment building.”
The Switch is like the building’s receptionist 👩‍💼.
When Preethi wants to talk to Simran, she just tells the receptionist (Switch), who knows exactly where Simran’s room is.
That’s how they all communicate within the LAN using their Private IP addresses.
But here’s the catch: their Private IPs (room numbers) keep changing whenever they reconnect, so today Kabir might be “192.168.1.5,” tomorrow “192.168.1.8.” 🔄
Now, if any of them want to talk to the outside world (Internet) — say Kabir wants to watch Netflix — they need to go through the Router.
The Router is like the main gate of the apartment building 🏢.
It has the Public IP address, which is what the whole internet sees

Router

The Router in College 1 takes Simran’s private IP and translates it into a Public IP (like 122.168.432.23).
Now, her message can travel across the internet to College 2.
The Router in College 2 receives it, and delivers it inside using Shakti’s Private IP through the switch.

Story with Colleges 📚
In College 1, students (Preethi, Simran, Kabir, etc.) all have Private IPs (like 192.168.23.2). These are only valid inside their campus LAN.
In College 2, students (Shakti, Sushil, Majnu, etc.) also use Private IPs (like 192.168.23.2).

⚠️ Problem:

Private IPs are not globally unique. Simran in College 1 and Shakti in College 2 might both have the same Private IP (192.168.23.2). If Simran tried to send data directly, the internet would get confused:
“Which 192.168.23.2 do you mean? College 1 or College 2?” 🤔
Why the change to Public IP is necessary 🌍

That’s where the Router comes in. It takes the Private IP and translates it into a Public IP (like 122.168.432.23).
Public IPs are globally unique → No two devices on the internet will share the same Public IP at the same time.
This guarantees that data meant for Simran in College 1 actually goes to her college and not accidentally to Shakti in College 2. ✅

Did u know ur wifi acts as a switch and a router

Now Lets get to business What is "Web Development"

Client Server Architecture

⚙️ How it Actually Works in Networking Terms

• Client (Browser/Device) → Sends a request (like typing google.com).
• Server (Hosting machine somewhere on the internet) → Processes the request (fetches data, runs backend code).
• Response → Server sends back the result (webpage, video, search result).
• Protocols → HTTP/HTTPS are like the “language” both use to talk.

🍕 Example in Real Life
You open YouTube on your phone (Client).
Your request goes to YouTube’s servers (Server).
Server finds your video and sends it back.
You watch Majnu’s failed comedy skits online 🎥😂

🔑 Key Points

Client = asks (user side, browser, app)

Server = serves (stores data, runs backend logic)

Communication happens over the Internet using IP addresses, ports, and protocols.

Frontend (Client-side)

What the customer sees:(Imagine a Restaurant 🍔)
Menu card 🍽️ (HTML → structure)
Nice decorations ✨ (CSS → styling)
Waiter’s tricks 😎 (JavaScript → interactivity, like dropdowns, animations, etc.)
👉 This is what you see in your browser when you open a website.

Backend (Server-side) → The kitchen 👨‍🍳:

Chef cooks the food (Python, Java, Node.js, PHP, etc.)
Database = Fridge storing ingredients 🥦🥩 (MySQL, MongoDB, PostgreSQL)
The kitchen staff only works when the waiter (frontend) brings the order.
👉 This is where your data is processed, stored, and sent back to the frontend.

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