A script to check if a given port is open on the connecting host. IP ranges included are for cloudflare, replace with an array containing your proxy server IP ranges

portopen.php

<?php
// A script to check if a given port is open on the connecting host.
// IP ranges included are for cloudflare, replace with an array containing your proxy server IP ranges
// https://b303.me/portopen.php?port=80
header("Content-Type: application/json");
header("Access-Control-Allow-Origin: *");
function cidr_match($ip, $ranges) {
        $out = array();
        foreach ($ranges as $range) {
                list ($subnet, $bits) = explode('/', $range);
                $ip = ip2long($ip);
                $subnet = ip2long($subnet);
                $mask = -1 << (32 - $bits);
                $subnet &= $mask; # nb: in case the supplied subnet wasn't correctly aligned
                array_push($out, ($ip & $mask) == $subnet);
        }
        return $out;
}
function get_ip() {
        $ranges = array("103.21.244.0/22","103.22.200.0/22","103.31.4.0/22",
                "104.16.0.0/12","108.162.192.0/18","131.0.72.0/22",
                "141.101.64.0/18","162.158.0.0/15","172.64.0.0/13",
                "173.245.48.0/20","188.114.96.0/20","190.93.240.0/20",
                "197.234.240.0/22","198.41.128.0/17","199.27.128.0/21",
                "127.0.0.0/8");
        if ( isset($_SERVER["HTTP_X_FORWARDED_FOR"]) && count(array_unique(cidr_match($_SERVER["HTTP_X_FORWARDED_FOR"], $ranges))) === 1 ) {
                $ip = $_SERVER["HTTP_X_FORWARDED_FOR"];
        } else {
                $ip = $_SERVER["REMOTE_ADDR"];
        }
        return $ip;
}
function check_port($ip, $port) {
        $connection = @fsockopen($ip, $port, $errno, $errstr, 1);
        if (is_resource($connection)) {
                fclose($connection);
                return true;
        } else {
                return false;
        }
}
if (!isset($_GET["port"])) {
        die(json_encode(array("error" => "Specify port parameter"), JSON_PRETTY_PRINT));
}
if (!is_numeric($_GET["port"])) {
        die(json_encode(array("error" => "Numbers only please"), JSON_PRETTY_PRINT));
}
$ip = get_ip();
echo json_encode(
        array(
                "host" => $ip,
                "port" => intval($_GET["port"]),
                "open" => check_port(get_ip(), intval($_GET["port"]))
        ),
        JSON_PRETTY_PRINT
);