Refactored HandleNewUser to use only one byte array variable for the entire scope and to use a switch statement on the ConnectionState. Behaves exactly as before, I just optimized the code to minimize the number of if statements and variable declarations.
Reorganized and cleaned up SystemServer using CodeMaid
Added some extension methods for some of our most common types. Refactored the user signup to use a stringbuilder for command input (it's more optimized for this task than the System.String is), also constraining username input to only alphabet characters and a max length of 15.