mcpgame.js

var io;
var socket;

module.exports.initGame = function(aIO, aSocket) {
    console.log('initGame...');
    io = aIO;
    socket = aSocket;

    if (!io) {
        console.log('io == null!');
        return;
    }
    if (!aSocket) {
        console.log('socket == null!');
        return;
    }
    
    socket.on('ping', onPing);

    return;

    var id = Math.trunc(Math.random() * 999);
    var userName = 'user_' + id;
    console.log(userName + ' connected');

    socket.broadcast.emit('chat msg', 'User ' + userName + ' connected...');

    socket.on('chat msg', (msg) => {
        console.log('message: ' + msg);
        io.emit('chat msg', userName + ': ' + msg);
    });

    socket.on('disconnect', () => {
        socket.broadcast.emit('chat msg', 'User ' + userName + ' disconnected...');
        console.log(userName + ' disconnected');
    });

}

function onPing() {
    socket.emit('pong');
}

server_game.js

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

const HOST = '127.0.0.1';
const PORT = process.env.port || '3000';

server.listen(PORT, () => {
    console.log(`Server started at http://${HOST}:${PORT}`);
});

var game = require('./logic/mcpgame');

io.on('connection', (socket) => {
    game.initGame(io, socket);
});