How do I setup my backend with DigitalOcean App Platform?

I have a relatively simple app, this is my first attempt at deploying a website, and it’s for my portfolio, so I apologize if this is elementary.

I had an express route setup to send an email from a form on the frontend, but I haven’t been able to get it to function since I’ve got it deployed on digitalOcean. relevant code below, let me know if I didn’t include information I should have! Thanks in advance!

Here’s the website… luce.codes.

This is the Index.js where the post route is.

var express = require(“express”);

var app = express();

require(“dotenv”).config();

const bodyParser = require(“body-parser”); const nodemailer = require(“nodemailer”); const cors = require(“cors”);

app.use(cors()); app.use(bodyParser.urlencoded({ extended: true })); app.use(bodyParser.json());

app.post(“/send_mail”, cors(), async (req, res) => { let { content, contact, name } = req.body; console.log(“response -------->”, req.body, content, contact, name);

var transporter = nodemailer.createTransport({ service: “gmail”, auth: { user: process.env.MAILFROM, pass: process.env.MAILPASS, }, }); var mailOptions = { from: contact, to: “dale@luce.codes”, subject: "luce.codes inquiry from " + name, text: contact + " <–contact----- " + "-----content-----> " + content, }; transporter.sendMail(mailOptions, function (error, info) { console.log(“this is in sendmail before if”); if (error) { console.log(error); } else { console.log("Email sent: " + info.response); } }); });

var server = app.listen(4000, function () { var host = server.address().address; var port = server.address().port; console.log(“i heard it all at http://%s:%s”, host, port); });

and here is where I am sending the info to the backend

const handleSubmit = async (evt) => { if (!disableButton(formState)) { setSent(true); try { const { contact, content, name } = formState; await axios.post(“http://localhost:4000/send_mail”, { contact, content, name, }); } catch (error) { console.log(error); } } else { alert(“Please complete the form before submitting!”); } };

and the error Im getting

AxiosError {message: ‘Network Error’, name: ‘AxiosError’, code: ‘ERR_NETWORK’, config: {…}, request: XMLHttpRequest, …} code: “ERR_NETWORK” config: {transitional: {…}, transformRequest: Array(1), transformResponse: Array(1), timeout: 0, adapter: ƒ, …} message: “Network Error” name: “AxiosError” request: XMLHttpRequest {data: undefined, onreadystatechange: null, readyState: 4, timeout: 0, withCredentials: false, …} response: XMLHttpRequest {data: undefined, onreadystatechange: null, readyState: 4, timeout: 0, withCredentials: false, …} [[Prototype]]: Error

POST http://localhost:4000/send_mail net::ERR_CONNECTION_REFUSED