Version 6.5 is not released yet (but will be very soon).
See this post on how to test with a pre-build of the APM Server: Java agent 1.0.0 Release Candidate ready for testing
The Java agent currently does not support Vert.x applications, unfortunately. Check out the supported web technologies to see what's currently supported. You can also vote for Vert.x support in the survey we put up.