I found recently an other way. My vlc server streaming is running on Linux. So with a php code, you can check the process of eatch program:
$commande = "ps auxf";
$result = shell_exec($commande);
$result = explode("\n",$result);
And finaly with the array $result, you can count the number of process (number of line) where you found VLC. That's works for the multiple broadcast too. But this time you search the IP:port for exemple.
Anyway,
if VLC is not running, you have 0
if VLC is running and wrong, you have 7 process on linux
if VLC is running well, you have 10 process and 2 more porcess by streaming output. I mean, if you have 3 guys connected, you have 10+3x2 = 16 process.
It is possible to have more line or less if you add video filters or multiple output. But whatever, I use this for check my server and it works pretty well.
Have fun