repl.js

var net = require('net');

const evalToBuffer = d => {
  try {
    const result = eval(d.toString());
    return Buffer.from(result + '\n', "utf-8");
  } catch (e) {
    return Buffer.from(e + '\n', "utf-8");
  }
};

var server = net.createServer(function(socket) {
	socket.write('Go go go!\r\n');
  socket.on('data', d => socket.write(evalToBuffer(d)));
});

server.listen(1338, '127.0.0.1');