When using r2dbc-mysql, we should specify the db port, like r2dbc:mysql://10.2.3.4:3306/db. If we don't specify it,MysqlConnectionFactoryProvider insists it doesn't support the url. However, I think allowing port omission is reasonable and convenient. In fact, some other r2dbc drivers allow it and use the default port (3306) in that case. Personally, I and some of my colleagues have experienced this minor issue when changing r2dbc driver to jasync-sql.

I'll try to make a PR related this issue, soon.