Why does the request pipe includes the headers in this code? - node.js

Question

I have a strange situation regarding http server and piping request.
From my past experience, when piping the request object of a http server to a writable stream of some sort, it does not include the headers, just the payload.
Today however, I wrote some very simple code, and from some reason, I'm spending the past 2 hours trying to figure out why it writes the headers to the file (super confusing!)
Here's my code:
server = http.createServer((req, res) => {
f = '/tmp/dest'
console.log(`writing to ${f}`)
s = fs.createWriteStream(f)
req.pipe(s)
req.on('end', () => {
res.end("done")
})
})
server.listen(port)
I test this with the following curl command:
curl -XPOST -F 'data=#test.txt' localhost:8080
And this is what I'm getting when I'm reading /tmp/dest:
--------------------------993d19e02b7578ff
Content-Disposition: form-data; name="data"; filename="test.txt"
Content-Type: text/plain
hello - this is some text
--------------------------993d19e02b7578ff--
Why am I seeing the headers here? I expected it to only write the payload
I have a code I wrote about a year ago that streams directly to a file without the headers, I don't understand what's different, but this one did the trick:
imageRouter.post('/upload', async(req, res) => {
if(!req.is("image/*")) {
let errorMessage = `the /upload destination was hit, but content-type is ${req.get("Content-Type")}`;
console.log(errorMessage);
res.status(415).send(errorMessage);
return;
}
let imageType = req.get("Content-Type").split('/')[1];
let [ err, writeStream ] = await getWritableStream({ suffix: imageType });
if (err) {
console.log("error while trying to write", err);
return res.status(500).end();
}
let imageName = writeStream.getID();
req.on('end', () => {
req.unpipe();
writeStream.close();
res.json({
imageRelativeLink: `/images/${imageName}`,
imageFullLink: `${self_hostname}/images/${imageName}`
});
});
req.pipe(writeStream);
});
What's different? Why does my code from a year ago (last block) writes without the form-data/headers? The resulting file is only an image, without text, but this time (the first block) shows http headers in the resulting file

Answer 1

Instead of using pipe, try using on('data') and referring to req.data to pull off the contents. This will allow the http library to process the HTTP body format and handle the "headers" (really: form part descriptors) for you.
Node Streaming Consumer API
server = http.createServer((req, res) => {
f = '/tmp/dest'
console.log(`writing to ${f}`)
s = fs.createWriteStream(f)
req.on('data', chunk) => {
s.write(chunk);
}
req.on('end', () => {
s.close();
res.end("done")
})
})
server.listen(port)

Answer 2

As it turns out, I had a mistake in my understanding, and therefore made a mistake in my question.
What I thought were the headers, were actually http multipart specification. This is how curl uploads a file when used with this syntax.
What I actually needed was to change the way I test my code with curl to one of the following:
cat /path/to/test/file | curl -T - localhost:8080
# or
curl -T - localhost:8080 < /path/to/test/file
# or
curl -T /path-/to/test/file localhost:8080 < /path/to/test/file
Using the -T (or --upload-file) flag, curl uploads the file (or stdin) without wrapping it in an http form.