JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<body>
<script>
var scan = function(){ 
  var address = prompt("IP:port to scan?", "127.0.0.1:8000")
  var t0 = new Date()
  document.write(`Scanning ${address} at ${t0}...`)
  img = document.createElement("img")
	img.onerror = function(){
  	delta = new Date() - t0
  	console.log(address + " is " + ((delta<400)?"open!":"closed!"))
  }
	img.src = `http://${address}/test.gif`
}
scan()
</script>
</body>
</html>