projeto-hit/frontend/src/services/socket.js

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

// "undefined" means the URL will be computed from the `window.location` object
const URL = process.env.REACT_APP_BACKEND_URL

export const socket = io(URL, {
    path: "/api-ws/socketio",
    withCredentials: true,
    extraHeaders: {
        "my-custom-header": "abcd"
    },
    // transports: ['websocket',  'polling']
});