socket.emit not sending to all clients

Socket.io seems to be getting confused with its socket connections, preventing me from using socket.emit to send a message to all connected clients. Instead, it sends to just one out of the two (I only allow two connections).

const app = require('express')()
const http = require('http').createServer(app)
const constants = require('./constants')
const draft = require('./game/draft')
const io = require('socket.io')(http, {
    cors: {
        origin: "http://localhost:3000  ",
        methods: ["GET", "POST"]
      }
})

// auth middleware
io.use((socket, next) => {
    const username = socket.handshake.auth.username;
    if (!username) {
        return next(new Error("invalid username"));
    }
    socket.username = username;
    next();
});

io.on('connection', function (socket) {
    if (io.engine.clientsCount > constants.CONNECTION_LIMIT) {
        socket.emit('err', { message: 'reach the limit of connections' })
        socket.disconnect()
        console.log('Disconnected...')
        return
    }

    socket.broadcast.emit("user connected", {
        userID: socket.id,
        username: socket.username,
    });
    const users = [];
    for (let [id, socket] of io.of("/").sockets) {
      users.push({
        userID: id,
        username: socket.username,
      });
    }
    socket.emit("users", users);

     if (users.length === 2) {
         socket.emit('START_GAME', { message: 'both players have joined the lobby' })
    }
})

The expected behavior is for the above START_GAME message to go to both connected clients. What happens is that it only goes to one. I can actually send it to the other if I combine socket.emit with socket.broadcast.emit.

Seems like a genuine bug. Picture below:

pic of problem

[rfox12]

Probably what people are looking for would be here: https://socket.io/docs/v4/server-api/#server-sockets

io.sockets.emit("hi", "everyone");
// is equivalent to
io.of("/").emit("hi", "everyone");

[darrachequesne]

Here we go! https://github.com/socketio/socket.io-website/commit/2d13db7ed3c83aa5c1d4fc1d5ca6afc1ef2b189e