anandgeorge/app.js

## app.js
var io = require('socket.io').listen(8000),
	nicknames = {};

io.sockets.on('connection', function (socket) {
  socket.on('user message', function (msg) {
    socket.broadcast.emit('user message', socket.nickname, msg);
  });

  socket.on('nickname', function (nick, fn) {
    if (nicknames[nick]) {
      fn(true);
    } else {
      fn(false);
      nicknames[nick] = socket.nickname = nick;
      socket.broadcast.emit('announcement', nick + ' connected');
      io.sockets.emit('nicknames', nicknames);
    }
  });

  socket.on('disconnect', function () {
    if (!socket.nickname) return;

    delete nicknames[socket.nickname];
    socket.broadcast.emit('announcement', socket.nickname + ' disconnected');
    socket.broadcast.emit('nicknames', nicknames);
  });
});

## client.html
<!DOCTYPE html>
<html>
  <head>
    <link href="style.css" rel="stylesheet">
    <script src="http://code.jquery.com/jquery-1.6.1.min.js"></script>
    <script src="/socket.io/socket.io.js"></script>
    <script>
      // socket.io specific code
      var socket = io.connect('http://localhost:8000');

      socket.on('connect', function () {
        $('#chat').addClass('connected');
      });

      socket.on('announcement', function (msg) {
        $('#lines').append($('<p>').append($('<em>').text(msg)));
      });

      socket.on('nicknames', function (nicknames) {
        $('#nicknames').empty().append($('<span>Online: </span>'));
        for (var i in nicknames) {
          $('#nicknames').append($('<b>').text(nicknames[i]));
        }
      });

      socket.on('user message', message);
      socket.on('reconnect', function () {
        $('#lines').remove();
        message('System', 'Reconnected to the server');
      });

      socket.on('reconnecting', function () {
        message('System', 'Attempting to re-connect to the server');
      });

      socket.on('error', function (e) {
        message('System', e ? e : 'A unknown error occurred');
      });

      function message (from, msg) {
        $('#lines').append($('<p>').append($('<b>').text(from), msg));
      }

      // dom manipulation
      $(function () {
        $('#set-nickname').submit(function (ev) {
          socket.emit('nickname', $('#nick').val(), function (set) {
            if (!set) {
              clear();
              return $('#chat').addClass('nickname-set');
            }
            $('#nickname-err').css('visibility', 'visible');
          });
          return false;
        });

        $('#send-message').submit(function () {
          message('me', $('#message').val());
          socket.emit('user message', $('#message').val());
          clear();
          $('#lines').get(0).scrollTop = 10000000;
          return false;
        });

        function clear () {
          $('#message').val('').focus();
        };
      });
    </script>
  </head>
  <body>
    <div id="chat">
      <div id="nickname">
        <form id="set-nickname" class="wrap">
          <p>Please type in your nickname and press enter.</p>
          <input id="nick">
          <p id="nickname-err">Nickname already in use</p>
        </form>
      </div>
      <div id="connecting">
        <div class="wrap">Connecting to socket.io server</div>
      </div>
      <div id="messages">
        <div id="nicknames"></div>
        <div id="lines"></div>
      </div>
      <form id="send-message">
        <input id="message">
        <button>Send</button>
      </form>
    </div>
  </body>
</html>
	var io = require('socket.io').listen(8000),
	nicknames = {};

	io.sockets.on('connection', function (socket) {
	socket.on('user message', function (msg) {
	socket.broadcast.emit('user message', socket.nickname, msg);
	});

	socket.on('nickname', function (nick, fn) {
	if (nicknames[nick]) {
	fn(true);
	} else {
	fn(false);
	nicknames[nick] = socket.nickname = nick;
	socket.broadcast.emit('announcement', nick + ' connected');
	io.sockets.emit('nicknames', nicknames);
	}
	});

	socket.on('disconnect', function () {
	if (!socket.nickname) return;

	delete nicknames[socket.nickname];
	socket.broadcast.emit('announcement', socket.nickname + ' disconnected');
	socket.broadcast.emit('nicknames', nicknames);
	});
	});
	<!DOCTYPE html>
	<html>
	<head>
	<link href="style.css" rel="stylesheet">
	<script src="http://code.jquery.com/jquery-1.6.1.min.js"></script>
	<script src="/socket.io/socket.io.js"></script>
	<script>
	// socket.io specific code
	var socket = io.connect('http://localhost:8000');

	socket.on('connect', function () {
	$('#chat').addClass('connected');
	});

	socket.on('announcement', function (msg) {
	$('#lines').append($('<p>').append($('<em>').text(msg)));
	});

	socket.on('nicknames', function (nicknames) {
	$('#nicknames').empty().append($('<span>Online: </span>'));
	for (var i in nicknames) {
	$('#nicknames').append($('<b>').text(nicknames[i]));
	}
	});

	socket.on('user message', message);
	socket.on('reconnect', function () {
	$('#lines').remove();
	message('System', 'Reconnected to the server');
	});

	socket.on('reconnecting', function () {
	message('System', 'Attempting to re-connect to the server');
	});

	socket.on('error', function (e) {
	message('System', e ? e : 'A unknown error occurred');
	});

	function message (from, msg) {
	$('#lines').append($('<p>').append($('<b>').text(from), msg));
	}

	// dom manipulation
	$(function () {
	$('#set-nickname').submit(function (ev) {
	socket.emit('nickname', $('#nick').val(), function (set) {
	if (!set) {
	clear();
	return $('#chat').addClass('nickname-set');
	}
	$('#nickname-err').css('visibility', 'visible');
	});
	return false;
	});

	$('#send-message').submit(function () {
	message('me', $('#message').val());
	socket.emit('user message', $('#message').val());
	clear();
	$('#lines').get(0).scrollTop = 10000000;
	return false;
	});

	function clear () {
	$('#message').val('').focus();
	};
	});
	</script>
	</head>
	<body>
	<div id="chat">
	<div id="nickname">
	<form id="set-nickname" class="wrap">
	<p>Please type in your nickname and press enter.</p>
	<input id="nick">
	<p id="nickname-err">Nickname already in use</p>
	</form>
	</div>
	<div id="connecting">
	<div class="wrap">Connecting to socket.io server</div>
	</div>
	<div id="messages">
	<div id="nicknames"></div>
	<div id="lines"></div>
	</div>
	<form id="send-message">
	<input id="message">
	<button>Send</button>
	</form>
	</div>
	</body>
	</html>