13.md

13. Problem: Express WebSocket Integration

Problem Statement: Extend an existing Express application to include WebSocket support. Create a WebSocket server that echoes back any message it receives from a client. Implement an endpoint "/websocket" that serves an HTML page with JavaScript to establish a WebSocket connection.

Function Signature:

/**
 * WebSocket server for Express
 * @param {Object} server - HTTP server instance
 */
function setupWebSocket(server) {
  // Your implementation here
}

Expected Output:

• Clients should be able to establish a WebSocket connection to "/websocket".
• Messages sent by clients should be echoed back by the server.

Test Cases:

1. Establish a WebSocket connection and send a message; it should be echoed back.