Using Cardinal’s Nakama integration, your client can submit transactions and queries to Nakama, which will then be transmitted to Cardinal. Nakama will handle the complexity of signing and submitting transactions to Cardinal, and will return the transaction receipts to your client once it’s executed.

​
RPC (Remote Procedure Calls)

Both Cardinal queries and transactions are submitted to Nakama via RPCs. The Nakama client libraries provide a simple interface for making RPC calls. You can consult the official documentation (Unity example) for a guide on how to do this on your game engine/programming language of choice.

​
Cardinal Query via Nakama RPC

All Cardinal queries are automatically registered as a Nakama RPC endpoint with the same format as the REST API endpoint: query/game/<query_name>
The query_name is based on the name you passed in when registering the query on Cardinal’s main.go file. For example, if you registered a query with the name player-info, the RPC endpoint will be query/game/player-info.

​
Example

In this example, let’s first register a query on Cardinal with the name player-info.
/cardinal/main.go
package main

func main() {
	w, err := cardinal.NewWorld()
	if err != nil {
		log.Fatal().Err(err).Msg("")
	}
	
	// Register a query named "player-info"
	err = cardinal.RegisterQuery[query.PlayerInfoReq, query.PlayerInfoResp](
		w, "player-info", query.PlayerInfo, 
	)
	if err != nil {
		log.Fatal().Err(err).Msg("")
	}

	// ...
}
We can then call this query via Nakama’s RPC:
Unity/C# Example
var client = new Nakama.Client("http", "127.0.0.1", 7350, "defaultkey");

try
{
    var payload = new Dictionary<string, string> {{ "username", "CoolMage" }};
    var response = await client.RpcAsync(session, "query/game/player-info", payload.ToJson());
    Debug.Log("player-info query result:", response);
}
catch (ApiResponseException ex)
{
    Debug.LogFormat("Error: {0}", ex.Message);
}

​
Cardinal Transaction via Nakama RPC

Before you can submit a transaction to Cardinal, you need to complete 2 key steps:
  1. Create and authenticate a Nakama account
  2. Create a Persona to attach to the Nakama account.

​
Authenticating with Nakama

Nakama provides multiple authentication methods that you can easily setup with a few lines of code, such as email/password, device ID, Facebook, Google, etc. You can consult the official documentation (Unity example) for a guide on how to do this.

​
Creating a Persona

Once your client is authenticated using a Nakama account, you can claim a persona and attach it to the account. This is done by calling the nakama/claim-persona RPC endpoint. The nakama/claim-persona RPC endpoint takes in a JSON payload with a single parameter personaTag that corresponds to the persona tag you want to claim. 
{"personaTag": "the-persona-tag-you-want-to-claim"}

​
Example

Unity/C# Example
var client = new Nakama.Client("http", "127.0.0.1", 7350, "defaultkey");

// Authenticate with the Nakama server using Device Authentication.
var deviceId = PlayerPrefs.GetString("deviceId", SystemInfo.deviceUniqueIdentifier);
var session = await client.AuthenticateDeviceAsync(deviceId);

try
{
    var payload = new Dictionary<string, string> {{ "personaTag", "MyCoolPersonaTag" }};
    var response = await client.RpcAsync(session, "nakama/claim-persona", payload.ToJson());
}
catch (ApiResponseException ex)
{
    Debug.LogFormat("Error: {0}", ex.Message);
}

​
Submitting a Transaction

Now that you have authenticated with Nakama and have a persona attached to your account, you can submit a transaction to Cardinal. You don’t have to worry about signing the transaction, as Nakama will handle this for you. You just need to provide the message payload and Nakama will take care of the rest. All Cardinal transactions/messages are automatically registered as a Nakama RPC endpoint with the same format as the REST API endpoint: tx/game/<msg_name>
The msg_name is based on the name you passed in when constructing the messaging using NewMessageType in Cardinal. For example, if you registered a message with the name attack, the RPC endpoint will be tx/game/attack.

​
Example

In this example, let’s first define a message on Cardinal with the name attack.
/cardinal/msg/attack.go
package msg

type AttackMsg struct {
	Target string
}

type AttackMsgReply struct {
	Damage int
}

var Attack = cardinal.NewMessageType[AttackMsg, AttackMsgReply]("attack")
We can then submit this transaction/message via Nakama’s RPC:
Unity/C# Example
var client = new Nakama.Client("http", "127.0.0.1", 7350, "defaultkey");

try
{
    var payload = new Dictionary<string, string> {{ "Target", "CoolMage" }};
    var response = await client.RpcAsync(session, "tx/game/attack", payload.ToJson());
}
catch (ApiResponseException ex)
{
    Debug.LogFormat("Error: {0}", ex.Message);
}

​
Viewing Receipts and Events

Game clients can view events emitted in systems as well as the results of iterating over messages by listening for notifications from Nakama.

​
Example

The code to receive notifications will be different depending on the game engine/client you are using. Learn more about how to receive notifications for your game client at Nakama docs. Here are structs that can be used to deserialize notification information. Note, the Receipt.Result field is an arbitrary object that will depend on the exact messages you’ve defined in your game.
Unity/C# Example
using System;

public class CardinalEvent
{
    [Serializable]
    [SuppressMessage("ReSharper", "InconsistentNaming")]
    public struct Message
    {
        public string message;
    }
}

public class CardinalReceipt
{
    [Serializable]
    [SuppressMessage("ReSharper", "InconsistentNaming")]
    public struct TxHash
    {
        public string txHash;
    }

    [Serializable]
    [SuppressMessage("ReSharper", "InconsistentNaming")]
    public struct Errors
    {
        public string errors;
    }

    // The exact structure of this Result field will depend on the message you defined in your game.
    [Serializable]
    [SuppressMessage("ReSharper", "InconsistentNaming")]
    public struct Result
    {
        public string result;
    }
}
This code will listen for Nakama notifications and parse the notifications into receipts and events.
Unity/C# Example
var client = new Nakama.Client("http", "127.0.0.1", 7350, "defaultkey");
var socket = client.NewSocket();

bool appearOnline = true;
int connectionTimeout = 30;
await socket.ConnectAsync(Session, appearOnline, connectionTimeout);

socket.ReceivedNotification += notification =>
{
    if (notification.Subject == "receipt") {
        var cardinalReceipt = JsonUtility.FromJson<CardinalReceipt>(notification.Content);
        // The exact structure of cardinalReceipt.Result will be game specific
    } else if (notification.Subject == "event") {
        var cardinalEvent = JsonUtility.FromJson<CardinalEvent>(notification.Content);
        // The exact content and structure of cardinalEvent.Message will be game specific
    }
};