PROTOCOL

all numbers are packed unless stated otherwise
packed values are msb

strings are predefined sizes and are terminated at either
the boundary of the region or the first NUL character (0x0)

byte n is b.n
region n is r.n

---

byte the zero: 0xDE
byte the one: 0xAD
byte the two: packet id
byte the 3-6: total body length - uint

byte the bytes after the header octet bytes bytes:
    raw body data shoved next to each other with no separation

---    

client -> server
    id 0: registration attempt
        r.0 - username - string (max 8b)
        r.1 - pin      - ushort (max 9999)
       
    id 1: login attempt
        r.0 - username - string (max 8b)
        r.1 - pin      - ushort (max 9999)
       
    id 2: ctx change response
        r.0 - ack    - bool
        r.1 - ctx id - ushort
    
--- 
   
server -> client
    id 0: registration response
        r.0 - succeeded - bool
        r.1 - status    - string (max 16b)
    
    id 1: login response
        r.0 - succeeded - bool
        r.1 - user id   - ushort
        r.2 - status    - string (max 16b)
        
    id 2: ctx change request
        r.0 - ctx id - ushort