server_replace.js

const app = require('./server/app');
const debug = require('debug')('node-angular')
const http = require('http');

const normalizePort = val => {
    var port = parseInt(val, 10);

    if (isNaN(port)) {
        return val
    }

    if (port >= 0) {
        return port;
    }

    return false;
}

const onError = error => {
    if (error.syscall !== 'listen') {
        throw error;
    }
    const bind = typeof port === "string" ? "pipe " + port : "port " + port;
    switch (error.code) {
        case "EACCES":
            console.error(bind + " requires elevated privileges");
            process.exit(1);
            break;
        case "EADDRINUSE":
            console.error(bind + " is already in use");
            process.exit(1);
            break;
        default:
            throw error;
    }

};

const onListening = () => {
    const addr = server.address();
    const bind = typeof port === 'string' ? 'pipe ' + port : 'port ' + port;
    debug('Listening on ' + bind);
}

const port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

const server = http.createServer(app);
server.on('error', onError);
server.on('listening', onListening);
server.listen(port);