node.js scan open ports

nodejsScanPorts.js

// based on https://github.com/baalexander/node-portscanner/blob/master/lib/portscanner.js
const {Socket} = require('net');

function connect(port, host, timeout, callback) {

    let connectionRefused = false;

    const socket = new Socket();
    let status = null;
    let error = null;

    // Socket connection established, port is open
    socket.on('connect', function () {
        status = 'open';
        socket.destroy();
    });

    // If no response, assume port is not listening
    socket.setTimeout(timeout);
    socket.on('timeout', function () {
        status = 'closed';
        error = new Error('Timeout (' + timeout + 'ms) occurred waiting for ' + host + ':' + port + ' to be available');
        socket.destroy();
    });

    // Assuming the port is not open if an error. May need to refine based on
    // exception
    socket.on('error', function (exception) {
        if (exception.code !== 'ECONNREFUSED') {
            error = exception;
        } else {
            connectionRefused = true;
        }
        status = 'closed';
    });

    // Return after the socket has closed
    socket.on('close', function (exception) {
        if (exception && !connectionRefused) {
            error = error || exception;
        } else {
            error = null;
        }
        callback(error, status);
    });

    socket.connect(port, host);
}

async function connectAsync(port, host, timeout) {
    return new Promise(resolve => {
        connect(port, host, timeout, (error, status) => {
            resolve({error, status, port, host});
        });
    });
}

async function connectAsyncRange(fromPort, toPort, host, timeout) {
    const promises = [];
    for (let port = fromPort; port < toPort; port++) {
        promises.push(connectAsync(port, host, timeout));
    }
    return await Promise.all(promises);
}

// settings
const concurrentRequests = 100;
const host = '10.144.44.1';
const fromPort = 400;
const toPort = 65535;

(async () => {
    const allOpenPorts = [];
    for (let port = fromPort; port < toPort; port += concurrentRequests) {
        const result = await connectAsyncRange(port, Math.min(toPort, port + concurrentRequests), host, 400);
        const closedPorts = [];
        const openPorts = [];
        result.forEach(({error, status, port, host}) => {
            if (status === 'open') {
                openPorts.push(port);
                allOpenPorts.push(port);
            } else {
                if (error) {
                    closedPorts.push(`${port} error: ${error}`);
                } else {
                    closedPorts.push(port);
                }

            }
        });
        if (openPorts.length > 0) {
            console.log('opened ports: ', openPorts.join(', '));
        }
        if (closedPorts.length > 0) {
            console.log('closed ports: ', closedPorts.join(', '));
        }
    }

    console.log('all opened ports for host', host, ' in range', fromPort, '-', toPort, ':', allOpenPorts.join(', '));
})();