code: function onRequest(request, response) {
    var filename = path.join(__dirname, request.url);
  
    // Serving server.js from cache. Useful for microbenchmarks.
    if (request.url === cachedUrl) {
      if (response.push) {
        // Also push down the client js, since it's possible if the requester wants
        // one, they want both.
        var push = response.push('/client.js');
        push.writeHead(200);
        fs.createReadStream(path.join(__dirname, '/client.js')).pipe(push);
      }
      response.end(cachedFile);
    }
  
    // Reading file from disk if it exists and is safe.
    else if ((filename.indexOf(__dirname) === 0) && fs.existsSync(filename) && fs.statSync(filename).isFile()) {
      response.writeHead(200);
      var fileStream = fs.createReadStream(filename);
      fileStream.pipe(response);
      fileStream.on('finish',response.end);
    }
  
    // Example for testing large (boundary-sized) frames.
    else if (request.url === "/largeframe") {
      response.writeHead(200);
      var body = 'a';
      for (var i = 0; i < 14; i++) {
        body += body;
      }
      body = body + 'a';
      response.end(body);
    }
  
    // Otherwise responding with 404.
    else {
      response.writeHead(404);
      response.end();
    }
  }
docs: The callback to handle requests