for client:
server parses packets from left to right like this:
    [u16 length][u8 type][char *data]

    length: the length of the entire packet
    type:
        PACKET_ERROR        = 0
        PACKET_REGISTER     = 1
        PACKET_AUTHENTICATE = 2
        PACKET_JOIN         = 3
        PACKET_TEXT         = 4
        PACKET_LEAVE        = 5
    
    data:     bytes of data, what it could represent depends on the packet type
        (following layouts are layouts for data byte array)
		PACKET_REGISTER     : [char username[20]][char password[20]]
                PACKET_AUTHENTICATE : [char username[20]][char password[20]]
                PACKET_JOIN         : []
                PACKET_TEXT         :
                PACKET_LEAVE        :