runnuning echo server on Ubuntu - node.js

Question

I followed this tutorial to install the node.js on ubuntu and installation is successful. But when i type node echo-server.js i am getting following error:
module.js:340
throw err;
^
Error: Cannot find module '../../lib/ws/server'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Module.require (module.js:362:17)
at require (module.js:378:17)
at Object.<anonymous> (/home/jci/node/joyent-node-283d735/echo-server.js:2:10)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.runMain (module.js:487:10)
echo server code:
var sys = require("util")
, ws = require('../../lib/ws/server');
var server = ws.createServer({debug: true});
// Handle WebSocket Requests
server.addListener("connection", function(conn){
conn.send("Connection: "+conn.id);
conn.addListener("message", function(message){
conn.send("<"+conn.id+"> "+message);
if(message == "error"){
conn.emit("error", "test");
}
});
});
server.addListener("error", function(){
console.log(Array.prototype.join.call(arguments, ", "));
});
server.addListener("disconnected", function(conn){
server.broadcast("<"+conn.id+"> disconnected");
});
server.listen(8000);
But lib/ws/server is missing. But where do i get it from??
I don't have web socket server in my node.js installation i guess.
Thanks
Sneha