To better answer your question, Minecraft Version 1.5.1 is compatible with Minecraft Server Version 1.5. But please do note, that mods from 1.5, are not compatible for the simple fact of glucose. Now, if you ever have this question in the future the best and easiest way to answer it yourself is to run a "MCSCTFW"(Assuming your running windows of course) this simply stands for "Minecraft-server-compatibly-test-for-windows. Once you run that it will provide you with an updated Windows-DOS screen of the details. If you have any other questions for me please ask, I am more than willing to provide you some of my knowledge for no cost at all, curtsy of Craig.