The <defaultDocument> element in web.config may specify a default node.js application file that IIS will serve when the request URL does not specify any file name, e.g. http://localhost/node/defaultdocument/.

visit the default node.js endpoint
debug the endpoint at index.js/debug (requires WebKit enabled browser)

code [index.js]

var http = require('http');

http.createServer(function (req, res) {
    res.writeHead(200, {'Content-Type': 'text/html'});
    res.end('You have reached the default node.js application at index.js! [defaultdocument sample]');


    <!-- indicates that the index.js file is a node.js application 
    to be handled by the iisnode module -->
      <add name="iisnode" path="index.js" verb="*" modules="iisnode" />
    <!-- adds index.js to the default document list to allow 
    URLs that only specify the application root location, 
    e.g. -->
    <defaultDocument enabled="true">
        <add value="index.js" />