expressjs measure transferred data code example

Example 1: http header express

app.get('/', (req, res) => {
  req.header('User-Agent')
})
// Use the Request.header() method to access
//one individual request header’s value

Example 2: express js continous GET /json/version

probably you are using chrome, if so,
goto: chrome://inspect/#devices
click on "Open dedicated DevTools for Node"
remove your locahost:[port] from listening