vortex0.js

const net = require('net')
const socket = net.Socket

const HOST = "vortex.labs.overthewire.org"
const PORT = 5842
const options = {
	readable: true,
	writable: true
}

client = new socket(options)
client.connect(PORT, HOST, () => {
	console.log('connected')
})
client.on('data', (data) => {
	console.log(data.toString(), '\n\n')
	let d = data.toString('hex')
   	let integers = [...Array(4)].map((_, i) => {
		let a = d.substr(i * 8, 8)
		return [...Array(4)]
			.map((_, i) => a.substr(i * 2, 2).split``.reverse().join``)
			.join``
			.split``
			.reverse()
			.join``
	})
	let sum = addHex(...integers)
	console.log(d, d.length, integers)
	client.write(sum)
});

function addHex(...hex_nums) {
	return hex_nums.reduce((a, c) => a + parseInt(c, 16), 0).toString(16)
}