1. What error messages does it spam you with?
2. I will look into the opening file / username issue later.
3. !@# is a 'word seperator' that I have created for seperating fields. The HamHost control panel system uses this.
4. I'm not worried if you decompiled the .jar file. It's all server-sided, so you can't find any exploits/hacks.
1 It spammed that the server had an error processing the request and that I should resend it or similar, restarting fixed it
2 Instead of saying that it can't open the file, make it tell the user "User does not exist"
3 Now enter "asdf!@#asdf!@#1234" in the username field and see how that's a bad idea
Not that they could do anything bad with it though
4 I didn't, I ran your executable in a sandbox (for obvious reasons) and traced what it sends