Socket.io sending messages - server

const express = require('express');
const socketIo = require('socket.io');
const http = require('http');
const app = express();
const port = 3000;

const server = http.createServer(app);
const io = socketIo(server);

io.on('connection', socket => {
    console.log('New client connected');
    socket.on('disconnect', () => console.log('Client disconnected'));

    // this message receive all connected clients
    io.sockets.emit('server_message', 'Welcome new client');

    socket.on('client_message', (message) => {
        console.log('client message message: ', message);
        // this message receive only actually connected client
        socket.emit('server_message', 'you: ' + message);
        // this message receive all users except actual
        socket.broadcast.emit('server_message', message);
    });
});

server.listen(port, () => console.log(`Listening on port ${port}`));