My system: Windows 11, Windows 10, and Ubuntu 22.04 clients run a Java application that accesses an AWS Aurora MySQL database.
What changed: Aurora was version 2.11.2 supporting MySQL 5.7. I upgraded it, to version 3.05.2 supporting MySQL 8. That involved also upgrading its EC2 instance from t2.small to t4g.medium.
The problem: After the upgrade, the Windows 10 clients timeout when trying to connect to the database. The Windows 11 and Ubuntu clients can still access it as normal.
Java reports this:
com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
Followed by a bunch of these:
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
Telnet reports this:
C:\Users\array>telnet production.<aws_account>.ap-southeast-2.rds.amazonaws.com 3306 Connecting To production.<aws_account>.ap-southeast-2.rds.amazonaws.com... Could not open connection to the host, on port 3306: Connect failed
I tried rebooting Aurora. No change.
I restored an SQLdump of the Aurora database to an AWS RDS MySQL Community database, version 8.0.35. Seems all clients can access that.
So this problem seems particular to Windows 10 clients and Aurora 3. There's a lot of Q&As about problems connecting to Aurora databases, but I can't find any specific to Windows 10.