security-guild-meetup-exercise-port-scanner.mjs

import { connect } from 'net';
import { once } from 'events';
import { Readable } from 'stream';

function* range(from, to) {
    for(let i = from; i < to; i++) yield i;
}
async function tryToConnectToPort(port, host) {
    const socket = connect(port, host);
    try {
        await once(socket, 'connect');
    } catch (e) {
        return false;
    } finally {
        socket.end();
    }
    return true;
}

const from = process.env.FROM_PORT ?? 2000;
const to = process.env.TO_PORT ?? 3000;
const concurrency = process.env.PARALLELISM ?? 100;
const status = await Readable.from(range(from, to)).map(async x => {
    const hasPortOpen = await tryToConnectToPort(x, process.env.HOST ?? '20.203.26.203');
    return { port: x, open: hasPortOpen };
}, { concurrency }).filter(x => x.open).toArray();

console.log("Port status", status)

Example output:

➜  node git:(master) ./out/Release/node ~/Desktop/scanner.mjs 
Port status [ { port: 2109, open: true } ]