client.js

var http = require('http')

var string = 'http://localhost:25000'

for(var count=0; count < process.argv[2]; count++) {
  http.get(string, (res) => {
    res.on('data', (d) => {
    });
    res.on('end', () => {
    })
  })
}

server.js

var http = require('http')

let count = 0
let intvl = 0

var data = 'g'.repeat(1024 * 1024 * 10)
var bytes = data.length
var server = http.createServer(function(req, res) {
  res.end(data, () => {
    count++;
  })
})

server.listen(25000, () => {
  console.log('server listening...')
})

setInterval(() => {
  intvl++
  console.log(`${bytes * count / (intvl * 1024 * 1024)} mbps`)
}, 1000)

usage:

$ node server.js
$ node client.js 200 in another terminal

output:
0 mbps
0 mbps
0 mbps
87.5 mbps
130 mbps
321.6666666666667 mbps
285.7142857142857 mbps
250 mbps
...