World Packet

World Packets are the majority of communication between the client and the world server.

World packets consist of a packet size, an Opcode and a body.

Headers

All world packet headers are encrypted using the session key negotiated during login, except for SMSG_AUTH_CHALLENGE and CMSG_AUTH_SESSION.

For server messages (SMSG) the headers look like:

SMSG Header

Offset	Size / Endianness	Type	Name	Description
0x0	2 / Big	uint16	size	Size of the packet including the opcode field.
0x2	2 / Little	uint16	opcode	Opcode for the packet. Determines the structure of the body.

For client messages (CMSG) the headers look like:

CMSG Header

Offset	Size / Endianness	Type	Name	Description
0x0	2 / Big	uint16	size	Size of the packet including the opcode field.
0x2	4 / Little	uint32	opcode	Opcode for the packet. Determines the structure of the body.

Process

World packets begin with the client making a TCP to the world server and then:

1. The server sends a SMSG_AUTH_CHALLENGE.
2. The client sends a CMSG_AUTH_SESSION.
3. The server sends a SMSG_AUTH_RESPONSE.
4. The client requests a character screen with CMSG_CHAR_ENUM.
5. The server responds with a list of characters in a SMSG_CHAR_ENUM.
6. The client is now at the character screen.