Troubleshoot RDS connection failures caused by a client problem by checking the following items:
In Windows, check whether the RDS instance port is enabled in the Windows security policy. In Linux, run iptables to check whether the RDS DB instance port is enabled in firewall settings.
Check whether the connection address, port parameter configuration, and JDBC connection parameter configuration are correct.
Check whether the username or password is correct if an error similar to the following occurs during RDS DB connection:
If the problem persists, contact post-sales technical support.