Proxy error (ECONNREFUSED) while trying to implement prebuilt Stripe checkout in web application using React and Node.js

Question

Proxy error: Could not proxy request /create-checkout-session from localhost:3000 to http://localhost:3000/ (ECONNREFUSED).

This is the error that I am getting above. I currently am following this guide on stripe: https://stripe.com/docs/checkout/quickstart#run-server using React and Node.js

I currently have a server.js file and a react component which acts as the checkout page

server.js

//server.js
const stripe = require('stripe')(
    process.env.NEXT_PUBLIC_STRIPE_API_KEY
    );
const express = require('express');
const app = express();
app.use(express.static('public'));

const YOUR_DOMAIN = 'http://localhost:3000';

app.post('/create-checkout-session', async (req, res) => {
  const session = await stripe.checkout.sessions.create({
    line_items: [
      {
        // Provide the exact Price ID (for example, pr_1234) of the product you want to sell
        price: process.env.NEXT_PUBLIC_STRIPE_PRICE_ID,
        quantity: 1,
      },
    ],
    mode: 'payment',
    success_url: 'https://localhost:3000/success',
    cancel_url: 'https://localhost:3000/cancel',
  });

  res.redirect(303, session.url);
});

app.listen(3000, () => console.log('Running on port 3000'));

CheckoutPage.jsx

//checkoutpage

import React, { useState, useEffect } from "react";

const ProductDisplay = () => (
  <section>
    <div>
      <img
        src="https://i.imgur.com/EHyR2nP.png"
        alt="The cover of Stubborn Attachments"
      />
      <div>
      <h3>Stubborn Attachments</h3>
      <h5>$20.00</h5>
      </div>
    </div>
    <form action="/create-checkout-session" method="POST">
      <button type="submit">
        Checkout
      </button>
    </form>
  </section>
);

const Message = ({ message }) => (
  <section>
    <p>{message}</p>
  </section>
);

const CheckoutPage = () => {
  const [message, setMessage] = useState("");

  useEffect(() => {
    // Check to see if this is a redirect back from Checkout
    const query = new URLSearchParams(window.location.search);

    if (query.get("success")) {
      setMessage("Order placed! You will receive an email confirmation.");
    }

    if (query.get("canceled")) {
      setMessage(
        "Order canceled -- continue to shop around and checkout when you're ready."
      );
    }
  }, []);

  return message ? (
    <Message message={message} />
  ) : (
    <ProductDisplay />
  );
}

export default CheckoutPage

I am thinking that something is wrong with the following code on the chekcoutpage.jsx file when trying to use this form element ` Checkout

`

I am expecting the button I press in the checkoutpage to redirect me to the prebuilt stripe checkout page for my product I have already set up my product in the stripe dashboard and got the necessary tokens in env file

I need help with getting the proxy to work

I tried adding "proxy": "http://localhost:3000/", in package.json file located in front end but it was not working