404 error with express and express-ws - node.js

Question

I'm having trouble trying to figure out why I'm getting this 404 error. I've gone through all the other questions on this site that cover 'express-ws' and i've modeled my code exactly how the solutions prescribed yet the websocket won't make a connection. I'm trying to create a websocket connection between my express server and react app. Below are previews of my code:
Express using express-ws (server.js):
var express = require('express');
var expressWs = require('express-ws');
var bodyParser = require('body-parser');
var cors = require('cors');
var nodemailer = require('nodemailer');
var email = require('./credentials');
var port = process.env.PORT || 3001;
var path = require('path');
// const WebSocket = require('ws');
// const http = require('http');
expressWs = expressWs(express());
let app = expressWs.app;
var server = require('http').createServer(app);
app.use(cors());
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
if (process.env.NODE_ENV === 'production') {
app.use(express.static('app/build'));
}
app.get('/', function(req, res){
console.log('server running!');
res.end();
});
app.ws('/ws', function(ws, req) {
console.log( 'socket running!' );
});
server.listen(port);
console.log('server started on port ' + port);
The GET route works fine but the ws route doesn't.
Call to express from React app:
componentDidMount() {
let ws = new WebSocket('ws://localhost:3001/ws');
ws.on( 'open', function open() {
console.log('app connected to websocket!');
} );
ws.on( 'message', function ( message ) {
console.log( message );
})
}
I've looked at all the following questions and don't understand why their solutions don't work for me:
Socket.IO 404 Error
express-ws connection problem
Node not working with express-ws
If anyone can let me know what's going on that would be great.

Answer 1

It seems your code does not follow express-ws's document. To use express-ws and make WebSocket endpoint, the code would be as:
var express = require('express');
var app = express();
var expressWs = require('express-ws')(app);
...
app.ws('/', function(ws, req) {
ws.on('message', function(msg) {
console.log(msg);
});
console.log('socket running');
});
app.listen(3000);
In the client side, ws object does not have field on. To listen WebSocket connection and message, you can use onopen and onmessage:
ws.onopen = function() {
console.log('app connected to websocket!');
};
ws.onmessage = function(message) {
console.log( message );
};

Answer 2

I had this exact problem and for me the solution was to change:
server.listen(port);
to:
app.listen(port);
I suspect what is going on is that express-ws is using the app listen function as its cue to start upgrading connections to ws and this won't happen if the server listen port occurs instead.