What are web sockets?

WebSockets are a protocol for bidirectional communication over a single TCP connection, allowing real-time data exchange between browser and server.

Main differences from traditional HTTP requests:

• Bidirectional communication: Server can send data to client without a prior request.
• Single connection: A long-lived connection is established, reducing overhead compared to creating new connections for each data exchange (as in HTTP).
• Reduced latency: Less time spent on connection setup, headers, and short request/response cycles.

How it works:

1. Handshake: Browser sends a special HTTP request to the server with headers Upgrade: websocket and Connection: Upgrade.
2. Connection establishment: If supported, server responds with 101 Switching Protocols, and the connection switches to WebSocket protocol.
3. Data transfer: Both sides can freely exchange messages in both directions at any time.

Use cases:

• Online games
• Chat and messaging apps
• Real-time data updates (quotes, news)
• Collaborative tools

Advantages:

• Low latency
• Efficient resource use (less overhead)
• Real-time bidirectional communication

Disadvantages:

• Requires support on client (browser) and server sides.
• More complex implementation than simple HTTP requests.

Client-side example in JavaScript:

// Create WebSocket
const socket = new WebSocket('wss://example.com/websocket');

// On open
socket.onopen = function(event) {
  console.log('Connection established');
  socket.send('Hello, server!'); // Send message
};

// On message
socket.onmessage = function(event) {
  console.log('Received message: ' + event.data);
};

// On close
socket.onclose = function(event) {
  if (event.wasClean) {
    console.log(`Closed cleanly, code=${event.code} reason=${event.reason}`);
  } else {
    console.log('Connection interrupted');
  }
};

// On error
socket.onerror = function(error) {
  console.error(`WebSocket error: ${error}`);
};

// To close
// socket.close();