tcp-test.js

// check TCP connect to port/host
var sock = require('net').connect({ port: 443, host: '127.0.0.1' }).on('connect', () => { console.log('connect OK'); sock.end(); }).on('error', (e) => { console.log('connect error (code:'+e.code+')'); })

// listen for TCP connect on port/host
var server = require('net').createServer((sock) => { console.log('client connected'); sock.end(); }).listen({ port: 443, host: '127.0.0.1' });