The body comes in boxes

1const http = require('node:http');2const server = http.createServer((req, res) => {3  let size = 0;4  console.log('handler starts');5  req.on('data', (chunk) => { size += chunk.length; });6  req.on('end', () => {7    console.log('body done: ' + size + ' bytes');8    res.end('thanks');9  });10  console.log('handler returns');11});12server.listen(0, async () => {13  const { port } = server.address();14  const res = await fetch(`http://localhost:${port}`, { method: 'POST', body: 'hello world' });15  console.log('client got ' + await res.text());16  server.close();17});