node.js - stuck on making simple web chat

It may sound strange, But I'm trying to make very simple web chat, and I need help..

I made this far with node -

var http = require('http');
var fs = require('fs');
var path = require('path');

var messages = [];

// Simple Function to load HTML/JavaScript/CSS Files
function LoadHTML(html, requrl, res) {
    var filePath = '.' + requrl;
    if (filePath == './') {
        filePath = './' + html;
    }

    var extname = path.extname(filePath);
    var contentType = 'text/html';
    switch (extname) {
        case '.js':
            contentType = 'text/javascript';
        break;
        case '.css':
            contentType = 'text/css';
        break;
    }

    fs.exists(filePath, function(exists) {

        if (exists) {
            fs.readFile(filePath, function(error, content) {
                if (error) {
                    res.writeHead(500);
                    res.end();
                }
                else {
                    res.writeHead(200, { 'Content-Type': contentType });
                    res.end(content, 'utf-8');
                }
            });
        }
        else {
            res.writeHead(404);
            res.end();
        }
    });  
}

http.createServer(function (req, res) {
    LoadHTML('index.html', req.url, res);
}).listen(8125);

The HTML/CSS I'm using - http://jsfiddle.net/yZ5at/

From here I'm stuck.. I want that when the user type something into the textarea and hit enter he's text will be shown in the chat div.

But how can I do that? any help please?