const net = require('net'); module.exports = function(port, callback) { const server = net.createServer(function(socket) { socket.write('Echo server\r\n'); socket.pipe(socket); }) server.listen(port, '127.0.0.1'); server.on('error', function (e) { callback(true) }) server.on('listening', function (e) { server.close() callback(false) }) }