Nostale Packets Help

Hi, I'm currently a college student looking to learn about encryption/decryption, my c++ knowledge is really bare bones but I have a decent amount of knowledge with java and c#, I am having a bit of trouble translating the crypto from the c++ thread into java, I was thinking something a long the lines of
Login Info as String ->to CharArray -> ParseInt as Hex -> Apply the offset -> turn it into a string -> Send back to server and I am at a loss as of where the sessionID comes from.

Thanks in advance for the help.

Look at opennos c# will be easier to convert into java than c++ (only the server part is done but client part isn't really difficult). But if you really want learn about encryption/decryption and not just translate it, I suggest you to learn how to use ollydbg(for exemple) in order to understand how encryption/decryption is done from the ASM(thats called reverse engineering)