Non-Standard UO Packets Repository

This repository is dedicated to documenting custom non-standard packets used by ClassicUO (web/desktop) and other external tools used to communicate with shards (e.g. the Freeshard protocol) Also provded are example/reference implementations for consuming the packets for various UO emulators.

The packet structures are described in YAML form using Kaitai Struct, a declarative language used for describing various binary data structures.

Packets

For each packet, you can access its Kaitai Struct definition (.ksy file) and a sample packet dump (.dump file under the samples directory).

1. WebIdentity Packet (dump)
   • Used by Shards on the Web Client for information about the user connecting via ClassicUO Web.
   • Contains a Secret known only by ClassicUO Web's Game Proxy and the Shard, which used to verify the packet is authentic. The client itself never sees the Secret.
   • The packet is sent as the 0xA4 SystemInfo packet. We chose to override the 0xA4 packet for the following reasons:
     • It's an unused packet, only sent by the OSI client, never by CUO itself. The packet handlers for ServUO/RunUO/MUO all read it, but ignore it.
     • All emulators (except Sphere) support receiving the packet before any Account/GameServer login making it a good candidate to add workarounds IP account limiters.
     • It's large enough for our use, and requires no Core modifications to enable receiving.

Packet Handler Implementations

This repository also includes implementations for handling the packets in various UO emulators. Please check the implementations directory. If your emulator does not have any implementation you may need to implement it yourself. If you do please open a pull request and we will add it to the repository.

Sample Packet Dumps

In the samples directory, you can find examples of raw packet dumps. These can be used in conjunction with the Kaitai Struct descriptions to test and experiment with the data structures.

To use a sample packet dump:

1. Download the sample you want to examine from the samples directory.
2. Open the Kaitai Web IDE.
3. In the Kaitai Web IDE, click on "Upload File" at the bottom left of the screen and select the .ksy packet and corresponding sample .dump (or drag and drop the files).
4. On the left hand file explorer double click the .ksy and .dump files.
5. The IDE should parse the binary data according to the structure defined in the .ksy file on the top left and display the parsed data below, with the hex data on the right.

Contribution

Your contributions are always welcome! Please read the contribution guidelines before submitting new packet structures or emulator implementations.

License

Please see the LICENSE file for details on the license.

---

For any questions or discussions, please open an issue on GitHub or reach us on the CUO Discord