> ## Documentation Index
> Fetch the complete documentation index at: https://nexus-core.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Get Started with Nexus Core

> Learn how to register your first DataAddon with Nexus Core v1.5.1, send a signed request, and receive a signed response in under 10 minutes.

This guide assumes Nexus Core is already installed and running. If not, follow the [Installation](/installation) guide first. By the end of this page, you will have a working DataAddon registered and a signed packet flowing from a Spigot server through Redis to MongoDB and back.

## Prerequisites

* Nexus Core v1.5.1 running with the web panel accessible at `http://localhost:8080`
* `NEXUS_SIGNING_KEY` set to the same value on Nexus Core and your Spigot server
* Redis and MongoDB connected (verified in the web panel)

## Steps

<Steps>
  <Step title="Create a DataAddon class">
    Create a class that extends `DataAddon`, implement the required methods, and annotate your document fields with `@DbDataModels`. The addon below stores player statistics in a `player_stats` MongoDB collection.

    ```java theme={null}
    package network.darkland.addons;

    import network.darkland.protocol.DataAddon;
    import network.darkland.protocol.NexusJsonDataContainer;
    import network.darkland.protocol.backup.annotations.DbDataModels;

    public class PlayerStatsAddon extends DataAddon {

        @Override
        public int addonId() {
            return 100; // Must be globally unique across all addons
        }

        @Override
        public String addonName() {
            return "Player Stats";
        }

        @Override
        public String getDatabase() {
            return "nexus_core_db";
        }

        @Override
        public String getCollection() {
            return "player_stats";
        }

        @Override
        public String cacheKeyHeaderTag() {
            return "stats"; // Redis key: "stats_<uuid>"
        }

        @DbDataModels(isId = true)
        private String uuid;

        @DbDataModels(defaultValue = "0", isId = false)
        private int kills;

        @DbDataModels(defaultValue = "0", isId = false)
        private int deaths;

        @DbDataModels(defaultValue = "0.0", isId = false)
        private double balance;

        @DbDataModels(defaultValue = "false", isId = false)
        private boolean isPremium;

        @Override
        public boolean handleRequest(String source, RequestType requestType,
                                     NexusJsonDataContainer data) {
            // Only allow deletes from the admin server
            if (requestType == RequestType.REMOVE_DATA) {
                return source.equals("admin");
            }
            return true;
        }
    }
    ```
  </Step>

  <Step title="Register the addon on startup">
    Register the addon with the protocol handler during your application startup:

    ```java theme={null}
    NexusApplication.getInstance()
        .getProtocolHandler()
        .registerAddon(new PlayerStatsAddon());
    ```

    Nexus Core now routes all requests for protocol ID `100` to the `player_stats` collection automatically.
  </Step>

  <Step title="Send a signed request from your Spigot server">
    On the Spigot side, construct a signed JSON packet and publish it to the Nexus Redis channel. As of v1.5.1, Nexus Core also signs its outgoing responses, so your client must be ready to verify the `sig`, `timestamp`, and `nonce` fields on the response.

    `GET_DATA` request:

    ```json theme={null}
    {
      "protocol": 100,
      "source": "pvp-1",
      "type": "GET_DATA",
      "data": {
        "uuid": "550e8400-e29b-41d4-a716-446655440000"
      },
      "timestamp": 1756900000000,
      "nonce": "b7f2b1b0-4b3b-4e29-9e2b-6b8f2b1b0b7f",
      "sig": "<base64-hmac-sha256>"
    }
    ```

    Build the `sig` field by computing `HmacSHA256(NEXUS_SIGNING_KEY, allFieldsExceptSig)` and encoding the result as Base64.
  </Step>

  <Step title="Receive and verify the signed response">
    Nexus Core publishes the response to your server's Redis channel. Since v1.5.1, responses also include `timestamp`, `nonce`, and `sig` fields. Verify the signature before trusting the data:

    ```json theme={null}
    {
      "protocol": 100,
      "source": "nexus",
      "type": "BROADCAST",
      "target": "pvp-1",
      "data": {
        "uuid": "550e8400-e29b-41d4-a716-446655440000",
        "kills": 142,
        "deaths": 38,
        "balance": 2500.75,
        "isPremium": true
      },
      "timestamp": 1756900000123,
      "nonce": "a1b2c3d4-...",
      "sig": "<base64-hmac-sha256>"
    }
    ```
  </Step>
</Steps>

## Next Steps

<CardGroup cols={2}>
  <Card title="Building Addons" icon="puzzle-piece" href="/addons/overview">
    Learn how to define schemas, gate requests, and build production-ready addons.
  </Card>

  <Card title="Security" icon="shield-halved" href="/concepts/security">
    Understand symmetric HMAC signing on both inbound and outbound messages.
  </Card>
</CardGroup>


## Related topics

- [Configuring Nexus Core](/configuration.md)
- [Installing Nexus Core](/installation.md)
- [Nexus Core: Centralized Cache Orchestration for Minecraft](/index.md)
- [Nexus Core Changelog](/reference/changelog.md)
- [Request Types in Nexus Core](/concepts/request-types.md)