Trying to figure out how to determine http transfer progress accurately in Node,js

curl_request

curl -i -# -o /dev/null http://localhost:3000/

large_file_progress.coffee

fs = require 'fs'
path = require 'path'
http = require 'http'

httpServer = http.createServer()

filePath = "/Users/avi/Applications/Games/StarCraft II/Campaigns/Liberty.SC2Campaign/enUS.SC2Assets"

httpServer.on 'request', (req, res) ->
    fs.stat filePath, (err, stats) ->
        if err
            res.writeHead 500, {'Content-Type': 'text/plain'}
            res.end err.message
            return

        bytesSent = 0
        res.writeHead 200, {'Content-Length': stats.size}

        fileStream = fs.createReadStream filePath
        fileStream.on 'end', -> res.end()
        fileStream.on 'data', (data) ->
            res.write data
            bytesSent += data.length
            progress = (bytesSent / stats.size * 100).toFixed(2)
            process.stdout.write "Progress: #{progress}  \r"

httpServer.listen 3000
console.log 'Listening on port 3000'