What is WebSocket?

WebSocket is an application-layer protocol that provides a persistent, two-way connection between a client and a server.

In short: WebSocket lets a client and a server "talk" in real time.

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#Why WebSocket is needed

Plain HTTP works like this:

• the client sends a request
• the server responds
• the connection ends

This is inconvenient when you need to:

• get updates instantly
• exchange messages continuously
• avoid waiting for a new request from the client

WebSocket solves this problem.

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#The core idea of WebSocket

The connection is established once and stays open.

After that:

• the client can send data to the server at any moment
• the server can send data to the client without being asked

This is called a two-way (full-duplex) connection.

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#How WebSocket works (simplified)

1. The client connects to the server over HTTP
2. An "upgrade" happens - a switch from HTTP to WebSocket
3. A persistent connection is established
4. The client and server freely exchange messages

No repeated requests or waiting.

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#Where WebSocket is used

Typical examples:

• online chats
• messengers
• stock quotes
• online games
• real-time notifications
• collaborative editors (Google Docs and similar tools)

Anywhere minimal latency matters.

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#WebSocket vs HTTP (in short)

• HTTP
  • request → response
  • no persistent connection
  • the server cannot initiate sending data on its own
• WebSocket
  • persistent connection
  • the server can send data on its own
  • suits real-time use cases

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#A real-life example

HTTP is like corresponding by email: you write → you wait → you get a reply.

WebSocket is like a phone call or a chat: you can talk at any moment and get a reply right away.

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#Short answer for the interview

Remember this phrasing:

WebSocket is an application-layer protocol that establishes a persistent, two-way connection between a client and a server and is used to exchange data in real time.