测试端口是否已打开并使用PHP转发

Question

有什么方法可以测试特定端口是否已打开并使用PHP正确转发？具体来说，我该如何使用套接字通过给定端口连接到给定用户？

一个示例在WhatsMyIP.org/ports的“自定义端口测试”部分中。

Answer 1

我不确定“正确转发”是什么意思，但希望这个例子能解决这个问题：

$host = 'stackoverflow.com';
$ports = array(21, 25, 80, 81, 110, 443, 3306);

foreach ($ports as $port)
{
    $connection = @fsockopen($host, $port);

    if (is_resource($connection))
    {
        echo '<h2>' . $host . ':' . $port . ' ' . '(' . getservbyport($port, 'tcp') . ') is open.</h2>' . "\n";

        fclose($connection);
    }

    else
    {
        echo '<h2>' . $host . ':' . $port . ' is not responding.</h2>' . "\n";
    }
}

输出：

stackoverflow.com:21 is not responding.
stackoverflow.com:25 is not responding.
stackoverflow.com:80 (http) is open.
stackoverflow.com:81 is not responding.
stackoverflow.com:110 is not responding.
stackoverflow.com:443 is not responding.
stackoverflow.com:3306 is not responding.

有关 端口号的完整列表，请参见http://www.iana.org/assignments/port-
numbers
。