Sample code.

app.js

/**
 * Module dependencies.
 */
var express = require('express');
var user = require('./routes/user');
var media = require('./routes/media');

var app = express();

app.use(express.bodyParser());
app.use(express.methodOverride());

app.post('/media/upload', media.upload);
app.post('/users/register', user.register);
app.post('/users/login', user.login);

app.listen(3000);
console.log('Listening on port 3000');

media.js

var knox = require('knox');
var logger = require('../Logger').Logger();

var client = knox.createClient({
    .... put S3 stuff here ....
});

exports.list = function(req, res){
  res.send("respond with a resource");
};

exports.upload = function(req, res){
  var file = req.body.fileUpload;

  // Alter the path
  var newPath = file.name;

  // Save in S3
  client.putFile(file.path, newPath, null, function(err, res){
    if(err) {
      logger.logError("Failed to upload media", err);
    } else if( res.statusCode == 200 ){
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.write(JSON.stringify({'fileName': newPath, 'file': file}));
    }
  });
};

And the logs:

Line 18 in my code is line 16 here.

TypeError: Cannot read property 'name' of undefined
at exports.upload (/Users/mruno/Documents/git-clones/tinsle/server/routes/media.js:18:21)
at callbacks (/Users/mruno/Documents/git-clones/tinsle/server/node_modules/express/lib/router/index.js:161:37)