3. What are WebSockets?

Overview of WebSockets

WebSockets are a communication protocol that provides full-duplex (two-way) communication between a client (e.g., a web browser) and a server over a single TCP connection.
Unlike HTTP, which requires repeated request-response cycles, WebSockets keep the connection open, allowing real-time data exchange.
Once a WebSocket connection is established, both the client and server can send messages to each other at any time without needing to make new requests.

Persistent Connection: A single connection remains open for the lifetime of the communication, avoiding repeated setup overhead.
Real-Time Communication: Ideal for scenarios where updates need to be sent immediately, such as live chat or gaming.
Low Latency: Messages are sent directly over the WebSocket connection, avoiding the delays of HTTP request-response cycles.
Bidirectional Communication: Both the client and server can send data whenever necessary.

Handshake:
- Communication begins with an HTTP request from the client to the server, called the WebSocket handshake.
- If the server accepts the handshake, the connection is upgraded from HTTP to the WebSocket protocol.
- Example HTTP upgrade headers:
```
GET /chat HTTP/1.1
Host: example.com
Upgrade: websocket
Connection: Upgrade
```
Communication:
- After the handshake, both client and server can send messages directly over the connection.
- Messages can be small and lightweight, containing plain text, JSON, or binary data.
Closure:
- Either the client or server can close the WebSocket connection when communication is no longer needed.

Chat Applications: Real-time messaging between users.
Live Feeds: Stock prices, sports scores, or breaking news updates.
Online Gaming: Low-latency data exchange for multiplayer games.
Collaborative Tools: Applications like shared document editing where changes are instantly reflected for all users.
IoT Devices: Communication between devices and servers for real-time data monitoring.