rswiki-book/src/RuneScape-Protocol.md

RuneScape Protocol

The RuneScape Protocol is the protocol used for data transmission between the RuneScape client and server. The protocol changes with every revision, however, typically only the packet opcodes are changed, and possibly some new packets are added.

The entire protocol is generally separated into two sub-protocols:

• Login Protocol
• Game Protocol

Login Protocol

The Login Protocol is the protocol that is used to log a player into RuneScape. This protocol contains information that sets up the encryption for the entire session, using the ISAAC algorithm. The "login block" is encrypted using RSA to prevent third party programs from packet-sniffing the ISAAC cipher keys and breaking the session encryption for the purpose of monitoring, injecting, and generally sniffing packets.

Game Protocol

The Game Protocol is the protocol in which game action information is transmitted. The opcodes are encrypted using ISAAC in order to prevent third party programs from tampering with the stream. The game protocol is made up of packets that are structured like so:

for fixed-size packets:
    opcode, payload[size]

for variable-sized packets:
    opcode, size, payload[size]

The opcode of a game packet is basically an identifier for the type of game action that the packet represents. The size of the packet is the amount of bytes that the payload of the packet carries, and the payload is an array of bytes that holds the actual data (information) of the packet.

A fixed-size packet is a packet whose payload size does never change, and the size for the specified opcode is already known between both client and server. A variable-sized packet is a packet whose payload size changes according to the situation of the game session.