I have been searching high an low for this and have not been able to find a solution. I have the following code in the server:

import express from 'express';
import { createServer } from 'https';
import { Server } from "socket.io";
import fs from 'fs';

const app = express();

const credentials = {
        key: fs.readFileSync('../key.pem'),
        cert: fs.readFileSync('../cert.pem')
};

// create http/https server
const server = createServer(credentials, app);

const io = new Server(server);

io.on('connection', (socket) => {
  console.log('a user connected');
});

server.listen(3000, () => {
        console.log('listening on localhost:3000');
}); 

Now in the client side I have:

import { io } from "socket.io-client";
import fs from "fs";

const socket = io("https://localhost:3000", {
        rejectUnauthorized: false,
        ca: fs.readFileSync("../cert.pem") 
});

socket.on("connect", () => console.log("connected to server"));

If I change the server side to import to:

import { createServer } from 'http'; 

instead of:

import { createServer } from 'https'; 

and I change the client side to:

const socket = io("http://localhost:3000"); 

instead of:

const socket = io("https://localhost:3000"); 

I socket io is able to communicate just fine

It is just the https. I tried to add certs and to set

rejectUnauthorized: false

with no avail. I found this question, but nothing there has worked. The socket io documentation has not been much help. What can I try next?