adb server version doesn't match this client

Question

Whenever I try to run adb devices:

            $ adb devices
            * daemon not running. starting it now *
            * daemon started su         


        

Answer 1

I find I occasionally need to explicitly kill and restart the server manually:

adb kill-server
adb start-server

This shock is generally enough to get it back on its feet again, and prevents repeated adb server is out of date. killing... messages.