Q.) It says 'outdated server'. _____A #1.) I made a video on how to update the server: http://www.youtube.com/watch?v=UhJCqU... _____A #2.) Make sure you are running the latest version of minecraft, you can do that by checking 'force update' before you log in. Then go back to minecraft.net and re-download to 'minecraft_server.jar'.
Q.) How do I put mods in the server? _____A.) Technically, this type of server does not support mods, but a CraftBukkit server can. I recently made a video on how to make one, check it out: http://www.youtube.com/watch?v=IBdeUt...
Q.) Do I need hamachi? _____A.) Yes, unless you want to port forward (that is a different story). The person joining will need it too.
Q.) It says 'User Not Premium' _____A.) I can't say I support this, but go into the 'server.properties' and change 'online-mode' to 'false'.
Q.) How do I make myself an admin (op)? _____A.) Make sure the server is not running, and put your minecraft username in the file called 'ops.txt' which is inside the 'server' folder.
Q.) How do I change the difficulty? _____A.) In the server.properties, find the one that says 'difficulty' and change it to one of these numbers: 0 - Peaceful 1 - Easy [default] 2 - Normal 3 - Hard
Q.) How do I change the game-mode? _____A.) In the server.properties, find the one that says 'gamemode' and change it to one of these numbers: 0 - Survival [default] , 1 - Creative
Q.) I don't like my world, how do I change it? _____A.) You just delete the 'world' folder that is inside your 'server' folder, this will randomly generate another new world.
Q.) How do I add more ram? _____A.) Open up the 'start.command' with text edit and change the two numbers (as shown in the video) to one of these intervals: .5GB= 512M Now, notice how there is a 'M' after '512', this means mb, not gb, so if you just change it to 512 it will be '512 gb' so you will need to change the 'G' after both the 'M'. If you want to make it more than 1gb, then just change the number itself. (It comes default as 1GB) So you can increase that to whatever you want, as long as you don't exceed or meet your computers' ram.
Q.) It says 'Invalid Server Key' _____A #1.) It is not the problem with the server itself, it is a bug in the server software. Open and close Minecraft a few times and connect and reconnect to the internet. I was also told that it has something to do with the map, for example: If you put in a Beta 1.8.1 world, it will work fine, but if you use a 1.0.0 world, it gives you the error. Look for 'A #2' for another solution.