just startup the convertData.bat
it will ask you for you L2 install folder, and create 5 files
in the data folder.
now the server is ready to be started, however you also have
to adjust the client a bit so that it actually connects to
your server instead of the real ones.
to fix this start the updateIni.bat
it will also ask you for the L2 install folder and the server address
you want to use.
you can also put a hostname in here.
the tool will change your L2.ini file and make a backup of the
old one.
just put the ip of the persons server instead of yours
to connect to others