You can now configure your AWS Client VPN endpoint to use either the port 443 or the port 1194, with support for both TCP and UDP transmissions. New and existing endpoints are defaulted to use the port 443. However, you can now modify these endpoints to use the port 1194. If you cannot use the port 443, such as for security reasons, using the port 1194 gives you more flexibility. 

from Recent Announcements: https://aws.amazon.com/about-aws/whats-new/2020/01/aws-client-vpn-now-supports-port-configuration/