Ultima Online Protocol :: Encrypted Login Seed
Packet # Packet Name Length Client Server Obsolete
---- Encrypted Login Seed 0x0004 X X
Data Type Description
uint Seed The encryption seed for a particular client.

Packet Description:
This is a special packet sent by the client after it first connects to the server.
The packet is a 32-bit value sent to the server to be used with encrypted login packets, and is usually the user's IP address.
This packet is sent again before logging on to a game server to be used with the game encryption.