Rename your map file to server_level.dat and drag it into the folder where your server files are. It should replace the old one.
If he is making a custom server, can he use the .dat format? I thought the format was entirely up to the individual custom server, and how THAT is made.
Can someone tell me what to do?
If he is making a custom server, can he use the .dat format? I thought the format was entirely up to the individual custom server, and how THAT is made.