编码问题

var http = require('http')
var server = http.createServer();
server.on('request', function(req, res) {
  if(req.url === '/plain') {
    res.setHeader('Content-Type', 'text/plain; charset=utf-8')
    res.end('Hello 世界');
  } else if(req.url === '/html') {
    res.setHeader('Content-Type', 'text/html; charset=utf-8')
    res.end('<h1>hello 世界</h1>')
  } 
})
server.listen(3000, function() {
  console.log('server is running on port 3000...')
})