Howto check with fsockopen() if a OpenVPN server is reachable?

[cidero]

Hi,

 

I am currently writing a testscript to check various services for availability.

 

I use this to check a HTTP webserver:

$fp = @fsockopen($host, $port, $errno, $errstr, $timeout); 
stream_set_timeout($fp, 5);
    if (!$fp) { 
        $output .= "$errstr ($errno)\n"; 
    } else { 
        $out = "GET / HTTP/1.1\r\n"; 
        $out .= "Host: ".$host."\r\n"; 
        $out .= "Connection: Close\r\n\r\n"; 
        fwrite($fp, $out); 
        while (!feof($fp)) { 
            $output .= fgets($fp, 128); 
        } 
        @fclose($fp); 
    }

In return I get the HTML of the website in the $output variable. If I want to check a HTTPS webserver I just add a "ssl://" in front of the $host in the first line.

 

To check SSH, I do this:

{  $fp = @fsockopen($host, $port, $errno, $errstr, $timeout); 
stream_set_timeout($fp, 5);
    if (!$fp) { 
        $output .= "$errstr ($errno)\n"; 
    } else { 
        while (!feof($fp)) { 
            $output .= fgets($fp, 128); 
        } 
        @fclose($fp); 
    } 

In return I get the SSH welcome banner, for example “SSH-2.0-OpenSSH_4.3 “.

 

But how can I check OpenVPN servers? I guess the problem is that OpenVPN uses UDP instead of TCP. The php documentation about fsockopen() says that I have to put a "udp://" in front of the $host variable. But it doesn't work. I guess I have to send some kind of "Hello" message like in the HTTP example.

 

Does anyone have an idea? As an example, OpenVPN servers should listen on 216.218.211.158:8047 and 69.22.186.19:8047.

 

Thank you very much in advance,

Lars