Using Node Buffer or fileStream with formData file upload - angularjs

Question

Update: I have more or less solved the problem using multipart (app.use(multipart({uploadDir: __dirname + '/../uploads'}))from these instructions), but still don't know why my original code (below) fails.
There have been numerous variations on this question, and I have tried the ideas there without success. I'm using a file uploading directive (and have since tried another open source alternative) to send a binary file to a node server, that runs the following code (based on an SO answer I can't now refind):
exports.receive = function(req, res) {
var fitFileBuffer = new Buffer('');
// req.setEncoding("binary"); //doesn't help
req.on('data', function(chunk) {
fitFileBuffer = Buffer.concat([fitFileBuffer, chunk]);
});
req.on('end', function() {
fs.writeFileSync(
"today2.fit",
fitFileBuffer,
'binary');
res.send(200);
});
};
If I upload today.fit and compare to today2.fit, they have the same Kb of data, but are not identical, and subsequent code fails to process the file. Given that this happens with two pieces of third party code I suspect the problem lies with my code.
Here are the details from the client side of the POST being made

Answer 1

In the end, when I realised that I wanted to avoid saving to disk, I modified generalhenry's code with some stuff from busyboy's site and my own use of a Buffer:
exports.receive = function (req, res, next) {
var busboy = new Busboy({ headers: req.headers });
var fileBuffer = new Buffer('');
busboy.on('file', function(fieldname, file, filename, encoding, mimetype) {
file.on('data', function(data) {
console.log('File [' + fieldname + '] got ' + data.length + ' bytes');
fileBuffer = Buffer.concat([fileBuffer, data]);
});
file.on('end', function() {
console.log('File [' + fieldname + '] Finished');
genXmlFromString(fileBuffer.toString(), function(data) {
res.json(data);
});
});
});
busboy.on('finish', function() {
console.log("'finish'");
});
req.pipe(busboy);
};

Answer 2

UPDATE: the client post details helped. You're not posting a file stream (which would have worked) you're posting a form stream. The good news is there are good modules for handling form streams.
You'll need to pipe the request stream into a form handling stream (such as busboy) which will handle the ------WebKitFormBoundary. . . part and them give you the file(s) as stream(s)
https://github.com/mscdex/busboy
var Busboy = require('busboy');
exports.receive = function(req, res, next) {
var busboy = new Busboy({ headers: req.headers });
busboy.on('file', function(fieldname, file, filename, encoding, mimetype) {
var fileWriteStream = fs.createWriteStream('today2.fit');
file.pipe(fileWriteStream);
});
busbody.on('finish', function() {
res.send(201);
});
req.pipe(busboy);
};