make a directory, put this file in it, npm install socket.io, node van.js

van.js

'use strict';

var http = require('http');
var sio = require('socket.io');

var app = http.createServer(function (req, res) {
    if (req.url === '/') {
        res.writeHead(200, {
            'Content-Type': 'text/html'
        });
        res.write('<input id="val">&nbsp;<button id="button">Send</button>\n');
        res.write('<script src="/socket.io/socket.io.js"></script>\n');
        res.write('<script>\n');
        res.write('    var socket = io.connect();\n');
        res.write('    socket.on("van", function (data) {\n');
        res.write('        var h1 = document.createElement("h1");\n');
        res.write('        var p = document.createElement("p");\n');
        res.write('        h1.innerText = "Got Data";\n');
        res.write('        p.innerText = data;\n');
        res.write('        document.body.appendChild(h1);\n');
        res.write('        document.body.appendChild(p);\n');
        res.write('    });\n');
        res.write('    var button = document.getElementById("button");\n');
        res.write('    button.onclick = function () {\n');
        res.write('        var val = document.getElementById("val");\n');
        res.write('        socket.emit("some_data", val.value);\n');
        res.write('    };\n');
        res.write('</script>\n');
        res.end();
    } else {
        res.writeHead(404);
        res.end();
    }
});

var io = sio.listen(app);
app.listen(8000);

io.sockets.on('connection', function (socket) {
    socket.emit('van', 'connected!');
    socket.on('some_data', function (data) {
        console.log('got some_data:', data);
        socket.emit('van', data); // echo it back for fun
    });
});