I have a similar setup running; what I did was sending the session ID as a URL parameter, including the "bootstrap.inc" file, bootstrapping the database, and then looking up the info I needed.
Example where I've stored some info in the session:
require_once './includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);
if (@$_GET["sid"]) {
$_SESSION["sid"] = @$_GET["sid"];
}
if (@$_SESSION["sid"]) {
//Get the get username/role from the database
$result = db_query("SELECT session FROM {sessions}
WHERE uid > 0 and sid = '%s'", array(
$_SESSION["sid"],
)
);
while ($row = db_fetch_object($result)) {
$_SESSION += unserializesession($row->session);
}
}
function unserializesession($data) {
if (strlen( $data) == 0) {
return array();
}
// Match all the session keys and offsets.
preg_match_all('/(^|;|\})([a-zA-Z0-9_]+)\|/i', $data, $matchesarray, PREG_OFFSET_CAPTURE);
$returnArray = array();
$lastOffset = null;
$currentKey = '';
foreach ($matchesarray[2] as $value) {
$offset = $value[1];
if (!is_null($lastOffset)) {
$valueText = substr($data, $lastOffset, $offset - $lastOffset);
$returnArray[$currentKey] = unserialize($valueText);
}
$currentKey = $value[0];
$lastOffset = $offset + strlen($currentKey) + 1;
}
$valueText = substr($data, $lastOffset);
$returnArray[$currentKey] = unserialize($valueText);
return $returnArray;
}
drupal_bootstrap(DRUPAL_BOOTSTRAP_DATABASE);
?