Encounter error when storing values into Couchbase server

Sample code:
try {
// adjust these parameters to match your installation
$cb = new Couchbase(“http://{Server_IP}:8091”, {uid},{pwd},“plusv3-maintenance”, true);
$cb->set(“a”, 101);
var_dump($cb->get(“a”));
} catch (CouchbaseException $e) {
var_dump($e);
}

The error message:

object(CouchbaseLibcouchbaseException)#2 (7) { [“message”:protected]=> string(52) “Failed to store value to server: Operation timed out” [“string”:“Exception”:private]=> string(0) “” [“code”:protected]=> int(0) [“file”:protected]=> string(39) “C:\xampp\htdocs\beersample-php\test.php” [“line”:protected]=> int(8) [“trace”:“Exception”:private]=> array(1) { [0]=> array(6) { [“file”]=> string(39) “C:\xampp\htdocs\beersample-php\test.php” [“line”]=> int(8) [“function”]=> string(3) “set” [“class”]=> string(9) “Couchbase” [“type”]=> string(2) “->” [“args”]=> array(2) { [0]=> string(1) “a” [1]=> int(101) } } } [“previous”:“Exception”:private]=> NULL }