title: Socket.IO error 'listen()' method expects an 'http.Server' instance after moving to Express 3.0
body: <p>I began learning Node.js today and I'm a little stuck.</p>
  
  <p>Following <a href="http://www.tigoe.com/pcomp/code/arduinowiring/1096/" rel="nofollow noreferrer">this</a> example, I get the following error when I try executing the js file:</p>
  
  <pre><code>Warning: express.createServer() is deprecated, express
  applications no longer inherit from http.Server,
  please use:
  
    var express = require("express");
    var app = express();
  
  Socket.IO's `listen()` method expects an `http.Server` instance
  as its first parameter. Are you migrating from Express 2.x to 3.x?
  If so, check out the "Socket.IO compatibility" section at:
  https://github.com/visionmedia/express/wiki/Migrating-from-2.x-to-3.x
     info  - socket.io started
  </code></pre>
  
  <p>I don't know how to fix this.</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>Error resulting from Bill's modified code:</p>
  
  <pre><code>/home/sisko/NodeJS/nodeSerialServer/serialServer.js:24
  var app     =   express()
                  ^
  ReferenceError: express is not defined
      at Object.&lt;anonymous&gt; (/home/sisko/NodeJS/nodeSerialServer/serialServer.js:24:12)
      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:492:10)
      at process.startup.processNextTick.process._tickCallback (node.js:244:9)
  </code></pre>