When the client sends a packet to the server, the first byte encapsulates its opcode. This specific opcode is encrypted by the ISAAC PRNG initialized with dynamically generated seeds during the login block. The server decrypts it and associates the opcode to the packet's respective predefined size. If the packet does not contain a fixed size, the opcode will be followed by either a byte or a word - it varies per packet - for its proper size.
