Hello again! Minecart here. I would like to note that CraftBukkit is a better server hosting tool than your normal Minecarting manager. Though you'll have to set up a LogMeIn Hamatchi serer as normal, your friends can play whenever your offline. 

First you want to download CraftBukkit here. This download link is quite annoying, but it's free and somewhat easy, so you can do it. Next you want to open the CraftBukkit Server file that you downloaded. Then open up the server properties and put in the same IP address. 

Then go into your old server file. Take the IP address out of this server properties file. 

Go back into your CraftBukkit file and take out all the World files. Even the _end and _nether files. Then take your world file from your old server file and put it into the CraftBukkit file.

Make sure to put you and your friends down as server OPs and put yourself into the Permissions file. Open them both with Notepad. 

Now I am still figuring this out, so you can't use server commands. I will figure this out very, very soon since I use this on my servers. 

Now your users can log on when you aren't online! 

-Minecart