Socket.io v3.0.4 not connecting, v2.3 does work - node.js

Question

Summary
I have basic sample code which works in socket.io 2.3 which does not work in socket.io 3.0, I want to understand what I need to change.
Full Description
I have a node.js / react project and I wanted to use socket.io. To do this, I implemented the example code from this article, using socket.io v3.0.4, which follows.
Server side:
const http = require("http");
const socketIo = require("socket.io");
const port = process.env.PORT || 4001;
const index = require("./routes/index");
const app = express();
app.use(index);
const server = http.createServer(app);
const io = socketIo(server);
let interval;
io.on("connection", (socket) => {
console.log("New client connected");
if (interval) {
clearInterval(interval);
}
interval = setInterval(() => getApiAndEmit(socket), 1000);
socket.on("disconnect", () => {
console.log("Client disconnected");
clearInterval(interval);
});
});
const getApiAndEmit = socket => {
const response = new Date();
// Emitting a new message. Will be consumed by the client
socket.emit("FromAPI", response);
};
server.listen(port, () => console.log(`Listening on port ${port}`));
Client Side:
import React, { useState, useEffect } from "react";
import socketIOClient from "socket.io-client";
const ENDPOINT = "http://127.0.0.1:4001";
function App() {
const [response, setResponse] = useState("");
useEffect(() => {
const socket = socketIOClient(ENDPOINT);
socket.on("FromAPI", data => {
setResponse(data);
});
}, []);
return (
<p>
It's <time dateTime={response}>{response}</time>
</p>
);
}
export default App;
on the server, I was receiving the error
socket.io:client client close with reason ping timeout
which led me to this article, which implied a version issue.
Based on that, I've attempted a few things, but specifically, I was running socket.io and socket.io-client both version 3.0.4. I uninstalled and reinstalled v 2.3.0/2.3.1. It now works flawlessly.
So my question is: what do I need to change to make this work with the more recent version of socket.io.