Test connection to a hostname and port with PHP

port-test.php

<?php

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);

$domain = "smtp.gmail.com";
$port = 587;

if ($socket = stream_socket_client("tcp://{$domain}:{$port}", $errno, $errstr, 10)) {
    echo "stream_socket_client: Connection to {$domain}:{$port} successful!<br>";
} else {
    echo "stream_socket_client error ({$errno}): {$errstr}<br>";
}

if (fsockopen($domain, $port)) {
    echo "fsockopen: Connection to {$domain}:{$port} successful!<br>";
} else {
    echo "fsockopen error: ".error_get_last()['message']."<br>";
}