Socket.io messaging app not sending messages with express server - node.js

Question

I'm building a messaging feature with socket.io and a React frontend. With a socket.io only server it is working as expected, with the following code:
Socket.io server only
const io = require("socket.io")(5000, {
cors: {
origin: "http://localhost:3000",
methods: ["GET", "POST"],
},
});
io.on("connection", (socket) => {
const id = socket.handshake.query.id;
socket.join(id);
socket.on("send-message", ({ recipients, text }) => {
recipients.forEach((recipient) => {
const newRecipients = recipients.filter((r) => r !== recipient);
newRecipients.push(id);
socket.broadcast.to(recipient).emit("receive-message", {
recipients: newRecipients,
sender: id,
text,
});
});
});
});
I am trying to integrate with express. The server is starting with the code below but messaging is no longer working:
Express server
const express = require("express");
const socketIo = require("socket.io");
const cors = require("cors");
const PORT = process.env.PORT || 5000;
const app = express();
const http = app.listen(PORT, () =>
console.log(`🚀 Server ready at http://localhost:${PORT}`)
);
const io = socketIo(http, {
cors: {
origin: "http://localhost:3000",
methods: ["GET", "POST", "send-message", "receive-message"],
},
});
io.once("connection", (socket) => {
const id = socket.handshake.query.id;
socket.join(id);
socket.on("connect_error", (err) => {
console.log(`connect_error due to ${err.message}`);
});
socket.on("send-message", ({ recipients, text }) => {
recipients.forEach((recipient) => {
const newRecipients = recipients.filter((r) => r !== recipient);
newRecipients.push(id);
socket.broadcast.to(recipient).emit("receive-message", {
recipients: newRecipients,
sender: id,
text,
});
});
});
});
Running it locally for both instances in Chrome with a window and another incognito window open on localhost:3000

Answer 1

As described here on('connection') event on client side not work. Change it to on('connect');
// server-side
io.on("connection", (socket) => {
console.log(socket.id); // x8WIv7-mJelg7on_ALbx
});
// client-side
socket.on("connect", () => {
console.log(socket.id); // x8WIv7-mJelg7on_ALbx
});