http://cz2.php.net/fsockopen ?

fsockopen() returns a file pointer which may be used together with the other file functions (such as fgets(), fgetss(), fwrite(), fclose(), and feof()). If the call fails, it will return FALSE

$hostname = "poradna.net"; //Bez http://
$ports = array(80, 3306, 21, 5432);

foreach($ports as $port)
{
print $hostname;
print (fsockopen($hostname, $port, $errnum, $errstr, 2)) ? " má " : " nemá ";
print " aktivní port $port";
print "<br><br>";
}