WebSocket Overview

import { createHmac } from 'crypto';
import { io } from 'socket.io-client';

function wsAuthHeaders(tokenId: string, secret: string) {
  const timestamp = new Date().toISOString();
  const message = `${timestamp}\nGET\n/socket.io/?EIO=4&transport=websocket\n`;
  const signature = createHmac('sha256', Buffer.from(secret, 'base64'))
    .update(message)
    .digest('base64');
  return { 'lmts-api-key': tokenId, 'lmts-timestamp': timestamp, 'lmts-signature': signature };
}

const socket = io('wss://ws.limitless.exchange/markets', {
  transports: ['websocket'],
  extraHeaders: wsAuthHeaders(TOKEN_ID, SECRET),
});

// Socket.IO replays the original headers on reconnect, and their timestamp is
// stale by then. Re-sign before every attempt.
socket.io.on('reconnect_attempt', () => {
  socket.io.opts.extraHeaders = wsAuthHeaders(TOKEN_ID, SECRET);
});