qt与mysql的链接失败

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("localhost");
db.setPort(3306);
db.setDatabaseName("your_database");
db.setUserName("your_username");
db.setPassword("your_password");

sudo systemctl status mysql

sudo systemctl start mysql

sudo ufw status

sudo ufw allow 3306

SHOW GRANTS FOR 'your_username'@'localhost';
GRANT ALL PRIVILEGES ON your_database.* TO 'your_username'@'localhost';
FLUSH PRIVILEGES;

if (!QSqlDatabase::isDriverAvailable("QMYSQL")) {
    qDebug() << "MySQL driver not loaded";
}

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QSqlError>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setPort(3306);
    db.setDatabaseName("your_database");
    db.setUserName("your_username");
    db.setPassword("your_password");

    if (!db.open()) {
        qDebug() << "Error: connection with database failed";
        qDebug() << db.lastError().text();
    } else {
        qDebug() << "Database: connection ok";
    }

    return a.exec();
}