The user file is a binary file containing 1 entry per registered user.

Each entry has the following format:
ABBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBCCCCCCCCCCCCCD 
where A='F' if the entry is empty and 'U' if it is used 
B...B is a 32 bytes C-string (always ended by a '\0') containing a nickname. 
  => the longest nickname takes 31 chars 
C...C is a 16 bytes C-string (always ended by a '\0') containing a password. 
  => the longest password takes 15 chars 
D is a 1 byte value: D='O' if this nick is an operator, 
                     D='N' if this nick is a normal user,
                     D='V' if this nick is a VIP user,
                     D='M' if this nick is the master of the hub
                     D='b' if this nick is the bot
                     D='B' if this nick is the master bot
    only the master of the hub can modify configuration and user file remotely.


