NodeJS check local port

checkport.js

 var args = process.argv.slice(2);

if(args.length == 0){
  console.log('port required')
  process.exit(0)
}

var port = parseInt(args[0]);

var net = require('net');
var client = net.connect({port: port},
function() { 
  console.log('server alive');
  client.end();
})
.on('error',function(){
  console.log('server down');
})
;