_result.txt

% node server.js & node client.js
Server running
{
  "host": "localhost:4321",
  "accept": "application/json",
  "content-type": "application/json",
  "content-length": "37",
  "connection": "close"
}
body: [{"a":1,"b":true,"c":"x","d":"漢字"}]
33 characters
37 bytes

client.js

var request = require('request').defaults({
  baseUrl: 'http://localhost:4321'
});

request('/', {
  method: 'POST',
  body: {
    a: 1,
    b: true,
    c: 'x',
    d: '漢字'
  },
  json: true
}, function(err, res, body) {
  if (err) console.error(err);
});

server.js

var server = require('http').createServer(function(req, res) {
  var rawData = '';
  req.on('data', function(chunk) {
    rawData += chunk;
  }).on('end', function() {
    console.log('body: [' + rawData + ']');
    console.log(rawData.length + ' characters');
    console.log(Buffer.from(rawData, 'utf8').length + ' bytes');
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Hello World\n');
  });
  console.log(JSON.stringify(req.headers, null, '  '));
});
server.listen(4321, 'localhost', function() {
  console.log('Server running');
});