MySQL Connection Error

Based on the error message you're encountering, there are a few potential causes and solutions to consider:

1. Port mismatch: The error message mentions port 3308, which is not the default MySQL port (3306). Ensure that you're using the correct port number for your RDS instance. If you've configured a custom port, make sure you're using that in your connection string.

2. Security group configuration: Although you've mentioned verifying the security group settings, it's worth double-checking. Ensure that the security group associated with your RDS instance has an inbound rule allowing traffic on the correct port (3306 or your custom port) from your client's IP address or the appropriate security group if connecting from an EC2 instance.

3. Network connectivity: The error suggests a network-level issue. Verify that your client can reach the RDS instance. If you're connecting from outside the VPC, ensure that the DB instance is set to be publicly accessible.

4. Firewall restrictions: Check if there are any firewall rules on your client side or within your corporate network that might be blocking outbound connections to the RDS port.

5. VPC configuration: If your RDS instance is in a VPC, ensure that the VPC is properly configured with the necessary route tables and network ACLs to allow traffic to and from your client.

6. DNS resolution: Verify that your client can resolve the RDS endpoint (db.cligoucgy9f7.ap-south-1.rds.amazonaws.com). Try pinging or using nslookup to check if the DNS resolution is working correctly.

7. RDS instance status: Confirm that your RDS instance is in the "Available" state and not undergoing maintenance or other operations that might affect connectivity.

8. SSL/TLS requirements: If your RDS instance requires SSL/TLS connections, ensure that your client is configured to use SSL/TLS when connecting.

9. IAM database authentication: If you're using IAM database authentication, make sure your IAM user or role has the necessary permissions to connect to the RDS instance.

To further troubleshoot, you can try:

• Using a different MySQL client or command-line tool to isolate whether the issue is specific to your current client.
• Temporarily allowing all inbound traffic in the security group (for testing purposes only) to determine if it's a security group issue.
• Connecting from an EC2 instance within the same VPC to eliminate potential network-related issues.

If none of these solutions resolve the issue, you may want to contact AWS support for more in-depth troubleshooting, as there could be underlying infrastructure or configuration issues specific to your account or setup.
Sources
Troubleshooting connections to your MySQL DB instance - Amazon Relational Database Service
Connecting to a DB instance running the MySQL database engine - Amazon Relational Database Service
Finding the connection information for an RDS for MySQL DB instance - Amazon Relational Database Service
Troubleshoot Amazon RDS for MySQL and Amazon RDS for MariaDB Errors | AWS Database Blog