socket.io: Cross-Origin Request Blocked on Firefox

Question

I'm running a nodejs socket.io server on a raspberry pi, and a socket.io web client on Firefox.

But Firefox keeps giving me a Cross-Origin Request Blocked (Same Origin Policy Error).

    // nodeJS Server:
    var app = require('express')();
    var cors = require('cors');
    app.use(cors({origin: '*:*'}));
    var server = require('http').Server(app);
    var io = require('socket.io')(server);
    server.listen(3000);

    io.on('connection', function(socket) {
        socket.emit('announcements', { message: 'A new user jas joined!' });
    });
    

    //JS Browser client:
    const socket = io('ws://<INSERT_MY_EXTERNAL_IP>:3000');

    socket.on('connect', () => {
      socket.send('Hello!');
    });

I've also tried: io.origins(...), io.set("origin", ...), but those keep saying the functions origins and set are undefined.

Not sure what to do at this point.

Answer 1

You can pass in a cors prop when you initialize the server socket.

Pass in a config object with cors set to true , eg. cors: true or cors: { origin: '*' } .

Read more about thathere .

In action (only tested in LAN):

client.js

const socket = io('ws://localhost:3000');
socket.on('testing', res => { console.log(res) });

server.js

const app = require('express')()
const server = require('http').createServer(app)

const opts = { cors: { origin: '*' } }
const io = require('socket.io')(server, opts)

const cors = require('cors')
app.use(cors())

io.on('connection', (socket) => {
  console.log(`Client connected (id=${socket.id})`)

  socket.emit('testing', 123)

  socket.on('disconnect', () => {
    console.log(`Client disconnected (id=${socket.id})`)
  })
});

(
  port => server.listen(
    port, 
    () => console.log(`Express server running on port ${port}`)
  )
)(3000)