GS error - Serial error?

hello. after alot of years i didnt play mu i want make a server.
i have downloaded Season2 files and client.

i have success load server. i connect the server .. then i try log with acc i made

then its DC me.
i check in GS and i see "serial error......" etc

what should i do?
i am not good in codding so i cannot continue.

p.s.
can some one please write me where i put each ip.
i have router. i opend port and i did loopback.
in files i need to put my global ip ( ex: whatismyip.com)
and other files i need put lan ip : (from cmd > ipconfig)

go to ur files data/lang/kor or wtv u have/commonloc.cfg there is the serial then copy it
and open mian.exe with maincracker.exe then ull seee the serial open again main.exe with hex editor search the serial of the main.exe and replace with the one u got on data/lang ..