Nakama Unreal Client Guide #

This client library guide will show you how to use the core Nakama features in Unreal by showing you how to develop the Nakama specific parts (without full game logic or UI) of an Among Us (external) inspired game called Sagi-shi (Japanese for “Imposter”).

Sagi-shi gameplay screen
Sagi-shi gameplay
Console Support
The Unreal SDK includes console support for Sony, Microsoft, and Nintendo platforms.

Prerequisites #

Before proceeding ensure that you have:

Installation #

The client is available from the:

For full instructions on how to setup your Unreal project and install the Nakama Unreal SDK please view the Nakama Unreal SDK README on GitHub.

Updates #

New versions of the Nakama Unreal Client and the corresponding improvements are documented in the Changelog.

TFunction Support
As of Nakama Unreal v2.9.0, TFunction support is available, meaning you can now use lambdas as callbacks for all API calls.

Asynchronous programming #

Many of the Nakama APIs are asynchronous and non-blocking.

Sagi-shi calls these methods in a way which does not block the calling thread so that the game is responsive and efficient.

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FOnAuthUpdate AuthenticationSuccessDelegate;
AuthenticationSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAuthenticationSuccess);

FOnError AuthenticationErrorDelegate;
AuthenticationErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAuthenticationError);

FString DeviceId = TEXT("<DeviceId>");
FString Username = TEXT("NewUser");
bool bCreate = true;
TMap<FString, FString> Vars;
Client->AuthenticateDevice(DeviceId, Username, Create, Vars, AuthenticationSuccessDelegate, AuthenticationErrorDelegate);

/* Define callbacks */

void ASagiShiActor::OnAuthenticationSuccess(UNakamaSession* LoginData)
{
    UE_Log(LogTemp, Log, TEXT("Login successful: %s"), *LoginData->SessionData.Username);
}

void ASagiShiActor::OnAuthenticationError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Failed to login: %s"), *Error.Message);
}

Handling exceptions #

Network programming requires additional safeguarding against connection and payload issues.

API calls in Sagi-shi gracefully handle errors:

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// Define the error handler function
void ASagiShiActor::OnError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("An error occurred: %s"), *Error.Message);

    if (Error == ENakamaErrorCode::ConnectionError)
    {
        UE_LOG(LogTemp, Error, TEXT("The server is currently unavailable. Check internet connection"));
    }
}

// Declare an error handler delegate and bind it to the error handler function
FOnError ErrorDelegate;
ErrorDelegate.AddDynamic(this, &ASagiShiActor::OnError);

// Pass the error delegate to the API function call
Client->GetUserAccount(Session, SuccessDelegate, ErrorDelegate);

Serializing and deserializing data #

This guide makes use of JSON serialization and deserialization using the built in JSON utilities inside Unreal Engine.

To use them you must ensure you have included them in your *.build.cs file as follows:

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PublicDependencyModuleNames.AddRange(new string[] { "Json", "JsonUtilities" });

First define a struct for your data (You can do this in the .h file for your Actor):

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USTRUCT()
struct FPlayer
{
    GENERATED_BODY()

public:
    UPROPERTY()
    FString Username;

    UPROPERTY()
    uint8 Level;
}

To write the struct to an FString (be sure to #include "JsonObjectConverter.h"):

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FPlayer Player { "PlayerOne", 99 };
FString Json;
FJsonObjectConverter::UStructToJsonObjectString(Player, Json);

To read from a JSON string into a struct:

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FString Json = TEXT("{\"username\": \"PlayerTwo\", \"level\": 10}");
FPlayer PlayerTwo;
if (!FJsonObjectConverter::JsonObjectStringToUStruct(Json, &PlayerTwo))
{
    // Error deserializing
}

Getting started #

Learn how to get started using the Nakama Client and Socket objects to start building Sagi-shi and your own game.

Nakama Client #

The Nakama Client connects to a Nakama Server and is the entry point to access Nakama features. It is recommended to have one client per server per game.

To create a client for Sagi-shi pass in your server connection details:

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FString ServerKey = TEXT("defaultkey");
FString Host = TEXT("127.0.0.1");
int32 Port = 7350;

Client = UNakamaClient::CreateDefaultClient(ServerKey, Host, Port);

Nakama Socket #

The Nakama Socket is used for gameplay and real-time latency-sensitive features such as chat, parties, matches and RPCs.

From the client create a real time client:

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RealtimeClient = Client->SetupRealtimeClient(Session);

FOnRealtimeClientConnected ConnectionSuccessDelegate;
ConnectionSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnRealtimeClientConnectionSuccess);

FOnRealtimeClientError ConnectionErrorDelegate;
ConnectionErrorDelegate.AddDynamic(this, &ASagiShiActor::OnRealtimeClientConnectionError);

RealtimeClient->Connect(ConnectionSuccessDelegate, ConnectionErrorDelegate);

/* Define callbacks */

void ASagiShiActor::OnRealtimeClientConnectionSuccess()
{
    UE_LOG(LogTemp, Log, TEXT("Socket connection succeeded."));
}

void ASagiShiActor::OnRealtimeClientConnectionError()
{
    UE_LOG(LogTemp, Log, TEXT("Socket connection failed."));
}

Authentication #

Nakama has many authentication methods and supports creating custom authentication on the server.

Sagi-shi will use device and Facebook authentication, linked to the same user account so that players can play from multiple devices.

Sagi-shi login screen
Login screen and Authentication options

Device authentication #

Nakama Device Authentication uses the physical device’s unique identifier to easily authenticate a user and create an account if one does not exist.

When using only device authentication, you don’t need a login UI as the player can automatically authenticate when the game launches.

Authentication is an example of a Nakama feature accessed from a Nakama Client instance.

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// Typically you would get the system's unique device identifier here.
FString DeviceId = TEXT("<DeviceId>");
FString Username = TEXT("<Username>");
bool bCreate = true;
TMap<FString, FString> Vars;

FOnAuthUpdate AuthenticationSuccessDelegate;
AuthenticationSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAuthenticationSuccess);

FOnError AuthenticationErrorDelegate;
AuthenticationErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAuthenticationError);

// Authenticate with the Nakama server using Device Authentication.
Client->AuthenticateDevice(DeviceId, Username, bCreate, Vars, AuthenticationSuccessDelegate, AuthenticationErrorDelegate);

Facebook authentication #

Nakama Facebook Authentication is an easy to use authentication method which lets you optionally import the player’s Facebook friends and add them to their Nakama Friends list.

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// Authenticate with the Nakama server using Facebook Authentication.
FString AccessToken = TEXT("<Token>");
FString Username = TEXT("<Username>");
bool bCreate = true;
bool bImportFriends = true;
TMap<FString, FString> Vars;

Client->AuthenticateFacebook(AccessToken, Username, bCreate, bImportFriends, Vars, AuthenticationSuccessDelegate, AuthenticationErrorDelegate);

Console authentication #

See the console authentication documentation for more information on how to authenticate players on consoles.

Custom authentication #

Nakama supports Custom Authentication methods to integrate with additional identity services.

See the Itch.io custom authentication recipe for an example.

Linking authentication #

Nakama allows players to Link Authentication methods to their account once they have authenticated.

Linking Device ID authentication

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FOnLinkSuccess LinkSuccessDelegate;
LinkSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnLinkSuccess);

FOnError LinkErrorDelegate;
LinkErrorDelegate.AddDynamic(this, &ASagiShiActor::OnLinkError);

// Link Device Authentication to existing player account.
Client->LinkDevice(Session, DeviceId, LinkSuccessDelegate, LinkErrorDelegate);

Linking Facebook authentication

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FOnLinkSuccess LinkSuccessDelegate;
LinkSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnLinkSuccess);

FOnError LinkErrorDelegate;
LinkErrorDelegate.AddDynamic(this, &ASagiShiActor::OnLinkError);

// Link Facebook Authentication to existing player account.
Client->LinkFacebook(Session, AccessToken, bImportFriends, LinkSuccessDelegate, LinkErrorDelegate);

Session variables #

Nakama Session Variables can be stored when authenticating and will be available on the client and server as long as the session is active.

Sagi-shi uses session variables to implement analytics, referral and rewards programs and more.

Store session variables by passing them as an argument when authenticating:

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TMap<FString, FString> Vars = {
    { "DeviceOS", "<OperatingSystem>" },
    { "DeviceModel", "<DeviceModel>" },
    { "GameVersion", "<GameVersion>" },
    { "InviterUserId", "<SomeUserId>" },
};

/// ...

Client->AuthenticateDevice(DeviceId, Username, bCreate, Vars, AuthenticationSuccessDelegate, AuthenticationErrorDelegate);

To access session variables:

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FString DeviceOs = Session->SessionData.Variables["DeviceOS"];

Session lifecycle #

Nakama Sessions expire after a time set in your server configuration. Expiring inactive sessions is a good security practice.

Nakama provides ways to restore sessions, for example when Sagi-shi players re-launch the game, or refresh tokens to keep the session active while the game is being played.

Use the auth and refresh tokens on the session object to restore or refresh sessions.

Store the tokens for use later:

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FString AuthToken = Session->SessionData.AuthToken;
FString RefreshToken = Session->SessionData.RefreshToken;

Restore a session without having to re-authenticate:

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Session->RestoreSession(authToken, refreshToken);

Check if a session has expired or is close to expiring and refresh it to keep it alive:

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// Check whether a session has expired or is close to expiry.
FDateTime Now = FDateNow::Now();
FDateTime In1Day = FDateTime::FromUnixTimestamp(Now.ToUnixTimestamp() + 24*60*60);
if (Session->IsExpired(FDateTime::Now()) || Session->IsExpired(In1Day))
{
    // Refresh the existing session (uses Nakama Core API)
    Client->Client->AuthenticateRefresh(Session->UserSession);
}

User accounts #

Nakama User Accounts store user information defined by Nakama and custom developer metadata.

Sagi-shi allows players to edit their accounts and stores metadata for things like game progression and in-game items.

Sagi-shi player profile screen
Player profile

Get the user account #

Many of Nakama’s features are accessible with an authenticated session, like fetching a user account.

Get a Sagi-shi player’s full user account with their basic user information and user id:

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FOnUserAccountInfo GetAccountSuccessDelegate;
GetAccountSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetAccountSuccess);

FOnError GetAccountErrorDelegate;
GetAccountErrorDelegate.AddDynamic(this, &ASagiShiActor::OnGetAccountError);

Client->GetUserAccount(Session, GetAccountSuccessDelegate, GetAccountErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetAccountSuccess(const FNakamaAccount& AccountData)
{
    FString Username = AccountData.User.Username;
    FString AvatarUrl = AccountData.User.AvatarUrl;
    FString UserId = AccountData.User.Id;
}

void ASagiShiActor::OnGetAccountError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Failed to get user account: %s"), *Error.Message);
}

Update the user account #

Nakama provides easy methods to update server stored resources like user accounts.

Sagi-shi players need to be able to update their public profiles:

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FOnUpdateAccount UpdateAccountSuccessDelegate;
UpdateAccountSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnUpdateAccountSuccess);

FOnError UpdateAccountErrorDelegate;
UpdateAccountErrorDelegate.AddDynamic(this, &ASagiShiActor::OnUpdateAccountError);

FString Username = Text("<NewUsername>");
FString DisplayName = Text("<NewDisplayName>");
FString AvatarUrl = Text("<NewAvatarUrl>");
FString LanguageTag = Text("<NewLanguageTag>");
FString Location = Text("<NewLocation>");
FString Timezone = Text("<NewTimezone>");
Client->UpdateAccount(Session, Username, DisplayName, AvatarUrl, LanguageTag, Location, Timezone, UpdateAccountSuccessDelegate, UpdateAccountErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnUpdateAccountSuccess()
{
    UE_LOG(LogTemp, Log, TEXT("Account successfully updated"));
}

void ASagiShiActor::OnUpdateAccountError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Failed to get user account: %s"), *Error.Message);
}

Getting users #

In addition to getting the current authenticated player’s user account, Nakama has a convenient way to get a list of other players’ public profiles from their ids or usernames.

Sagi-shi uses this method to display player profiles when engaging with other Nakama features:

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FOnGetUsers GetUsersSuccessDelegate;
GetUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetUsersSuccess);

FOnError GetUsersErrorDelegate;
GetUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnGetUsersError);

TArray<FString> UserIds = { TEXT("<AnotherUserId>") };
TArray<FString> Usernames = { TEXT("<AnotherUsername>") };
TArray<FString> FacebookIds = { TEXT("<AnotherFacebookId>") };

Client->GetUsers(Session, UserIds, Usernames, FacebookIds, GetUsersSuccessDelegate, GetUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetUsersSuccess(const TArray<FNakamaUser>& Users)
{
    UE_LOG(LogTemp, Log, TEXT("Successfully retrieved %d users", Users.Num()));
}

void ASagiShiActor::OnGetUsersError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Error retrieving users: %s"), *Error.Message);
}

Storing metadata #

Nakama User Metadata allows developers to extend user accounts with public user fields.

User metadata can only be updated on the server. See the updating user metadata recipe for an example.

Sagi-shi will use metadata to store what in-game items players have equipped:

Reading metadata #

Define a class that describes the metadata and parse the JSON metadata:

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USTRUCT()
struct FUserMetadata
{
    GENERATED_BODY()

public:
    UPROPERTY()
    FString Title;

    UPROPERTY()
    FString Hat;

    UPROPERTY()
    FString Skin;
}

FOnUserAccountInfo GetUserAccountSuccessDelegate;
GetUserAccountSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetUserAccountSuccess);

FOnError GetUserAccountErrorDelegate;
GetUserAccountErrorDelegate.AddDynamic(this, &ASagiShiActor::OnGetUserAccountError);

Client->GetUserAccount(Session, GetUserAccountSuccessDelegate, GetUserAccountErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetUserAccountSuccess(const FNakamaAccount& AccountData)
{
    FUserMetadata UserMetadata;
    FJsonObjectConverter::JsonObjectStringToUStruct(AccountData.User.Metadata, &UserMetadata);
    UE_LOG(LogTemp, Log, TEXT("Title: %s"), *UserMetadata.Title);
    UE_LOG(LogTemp, Log, TEXT("Hat: %s"), *UserMetadata.Hat);
    UE_LOG(LogTemp, Log, TEXT("Skin: %s"), *UserMetadata.Skin);
}

void ASagiShiActor::OnGetUserAccountError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Error retrieving metadata: %s"), *Error.Message);
}

Wallets #

Nakama User Wallets can store multiple digital currencies as key/value pairs of strings/integers.

Players in Sagi-shi can unlock or purchase titles, skins and hats with a virtual in-game currency.

Accessing wallets #

Parse the JSON wallet data from the user account:

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USTRUCT()
struct FUserWallet
{
    GENERATED_BODY()

public:
    int32 Coins;
}

void ASagiShiActor::OnGetUserAccountSuccess(const FNakamaAccount& AccountData)
{
    FUserWallet UserWallet;
    FJsonObjectConverter::JsonObjectStringToUStruct(AccountData.User.Wallet, &UserWallet);
    UE_LOG(LogTemp, Log, TEXT("Coins: %d"), UserWallet.Coins);
}

Updating wallets #

Wallets can only be updated on the server. See the user account virtual wallet documentation for an example.

Storage Engine #

The Nakama Storage Engine is a distributed and scalable document-based storage solution for your game.

The Storage Engine gives you more control over how data can be accessed and structured in collections.

Collections are named, and store JSON data under a unique key and the user id.

By default, the player has full permission to create, read, update and delete their own storage objects.

Sagi-shi players can unlock or purchase many items, which are stored in the Storage Engine.

Sagi-shi player items screen
Player items

Reading storage objects #

Define a class that describes the storage object and create a new storage object id with the collection name, key and user id. Finally, read the storage objects and parse the JSON data:

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USTRUCT()
struct FUnlocksStorageObject
{
    GENERATED_BODY()

public:
    UPROPERTY()
    TArray<FString> Hats;
}

FOnStorageObjectsRead ReadStorageObjectsSuccessDelegate;
ReadStorageObjectsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnReadStorageObjectsSuccess);

FOnError ReadStorageObjectsErrorDelegate;
ReadStorageObjectsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnReadStorageObjectsError);

FNakamaReadStorageObjectId Id;
Id.Collection = TEXT("Unlocks");
Id.Key = TEXT("Hats");
Id.UserId = Session->SessionData.UserId;
TArray<FNakamaReadStorageObjectId> StorageObjectIds = { Id };

Client->ReadStorageObjects(Session, StorageObjectIds, ReadStorageObjectsSuccessDelegate, ReadStorageObjectsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnReadStorageObjectsSuccess(const FNakamaStorageObjectList& StorageObjects)
{
	if (StorageObjects.Num() != 1)
    {
		UE_LOG(LogTemp, Warning, TEXT("Incorrect amount of storage objects %d."), StorageObjects.Num());	// Withoug opening the code I don't recall if this was the correct way of formatting strings, I think it is.
		return;
    }
	FUnlocksStorageObject HatsStorageObject;
	if (!FJsonObjectConverter::JsonObjectStringToUStruct(StorageObjects[0].Value, &HatsStorageObject, 0, 0))
	{
		UE_LOG(LogTemp, Warning, TEXT("Failed to deserialize storage object."));
	}
	UE_LOG(LogTemp, Log, TEXT("Unlocked Hats:"));
	for (int32 i = 0; i < HatsStorageObject.Items.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("%s"), *HatsStorageObject.Items[i]);
	}
}

void ASagiShiActor::OnReadStorageObjectsError(const FNakamaError& Error)
{
    UE_LOG(LogTemp, Error, TEXT("Error reading storage objects: %s"), *Error.Message);
}

To read other players’ public storage objects use their UserId instead. Remember that players can only read storage objects they own or that are public (PermissionRead value of 2).

Writing storage objects #

Nakama allows developers to write to the Storage Engine from the client and server.

Consider what adverse effects a malicious user can have on your game and economy when deciding where to put your write logic, for example data that should only be written authoritatively (i.e. game unlocks or progress).

Sagi-shi allows players to favorite items for easier access in the UI and it is safe to write this data from the client.

Create a write storage object with the collection name, key and JSON encoded data. Finally, write the storage objects to the Storage Engine:

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FUnlocksStorageObject HatsStorageObject;
HatsStorageObject.Items.Add(TEXT("cowboy"));
HatsStorageObject.Items.Add(TEXT("alien"));

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(HatsStorageObject, Json);

FNakamaStoreObjectWrite WriteObject;
WriteObject.Collection = "Unlocks";
WriteObject.Key = "Hats";
WriteObject.PermissionWrite = ENakamaStoragePermissionWrite::OWNER_WRITE;
WriteObject.PermissionRead = ENakamaStoragePermissionRead::OWNER_READ;
WriteObject.Value = Json;

TArray<FNakamaStoreObjectWrite> StorageObjectsData = { WriteObject };

FOnStorageObjectAcks WriteStorageObjectsSuccessDelegate;
WriteStorageObjectsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnWriteStorageObjectsSuccess);

FOnError WriteStorageObjectsErrorDelegate;
WriteStorageObjectsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnWriteStorageObjectsError);

Client->WriteStorageObjects(Session, StorageObjectsData, WriteStorageObjectsSuccessDelegate, WriteStorageObjectsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnWriteStorageObjectsSuccess(const FNakamaStoreObjectAcks& StorageObjectAcks)
{
	UE_LOG(LogTemp, Log, TEXT("Success writing storage object"));
}

void ASagiShiActor::OnWriteStorageObjectsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error writing storage object: %s"), *Error.Message);
}

You can also pass multiple write objects:

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TArray<FNakamaStoreObjectWrite> StorageObjectsData = { WriteObject1, WriteObject2, WriteObject3 };
Client->WriteStorageObjects(Session, StorageObjectsData, WriteStorageObjectsSuccessDelegate, WriteStorageObjectsErrorDelegate);

Conditional writes #

Storage Engine Conditional Writes ensure that write operations only happen if the object hasn’t changed since you accessed it.

This gives you protection from overwriting data, for example the Sagi-shi server could have updated an object since the player last accessed it.

To perform a conditional write, add a version to the write storage object with the most recent object version:

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// Assuming we already have a storage object (WriteObject).
FNakamaStoreObjectWrite WriteObject2;
WriteObject2.Collection = "Unlocks";
WriteObject2.Key = "Hats";
WriteObject2.PermissionWrite = ENakamaStoragePermissionWrite::OWNER_WRITE;
WriteObject2.PermissionRead = ENakamaStoragePermissionRead::OWNER_READ;
WriteObject2.Value = Json;
WriteObject2.Version = WriteObject.Version

TArray<FNakamaStoreObjectWrite> StorageObjectsData = { WriteObject2 };

Client->WriteStorageObjects(Session, StorageObjectsData, WriteStorageObjectsSuccessDelegate, WriteStorageObjectsErrorDelegate);

Listing storage objects #

Instead of doing multiple read requests with separate keys you can list all the storage objects the player has access to in a collection.

Sagi-shi lists all the player’s unlocked or purchased titles, hats and skins:

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FString Collection = TEXT("Unlocks");
int32 Limit = 3;
FString Cursor = TEXT("");

FOnStorageObjectsListed ListStorageObjectsSuccessDelegate;
ListStorageObjectsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListStorageObjectsSuccess);

FOnError ListStorageObjectsErrorDelegate;
ListStorageObjectsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListStorageObjectsError);

Client->ListStorageObjects(Session, Collection, Session->SessionData.UserId, Limit, Cursor, ListStorageObjectsSuccessDelegate, ListStorageObjectsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListStorageObjectsSuccess(const FNakamaStorageObjectList& StorageObjects)
{
	for (int16 i = 0; i < StorageObjects.Objects.Num(); i++)
	{
		FUnlocksStorageObject StorageObject;
		FJsonObjectConverter::JsonObjectStringToUStruct(StorageObjects.Objects[i].Value, &StorageObject);

		UE_LOG(LogTemp, Log, TEXT("%s Unlocks:"), *StorageObjects.Objects[i].Key);
		for (int16 x = 0; x < StorageObject.Items.Num(); x++)
		{
			UE_LOG(LogTemp, Log, TEXT("%s"), *StorageObject.Items[x]);
		}
	}
}

void ASagiShiActor::OnListStorageObjectsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error reading storage objects: %s"), *Error.Message);
}

Paginating results #

Nakama methods that list results return a cursor which can be passed to subsequent calls to Nakama to indicate where to start retrieving objects from in the collection.

For example:

  • If the cursor has a value of 5, you will get results from the fifth object.
  • If the cursor is null, you will get results from the first object.
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Client->ListStorageObjects(Session, Collection, Session->SessionData.UserId, Limit, StorageObjects.Cursor, ListStorageObjectsSuccessDelegate, ListStorageObjectsErrorDelegate);

Protecting storage operations on the server #

Nakama Storage Engine operations can be protected on the server to protect data the player shouldn’t be able to modify (i.e. game unlocks or progress). See the writing to the Storage Engine authoritatively recipe.

Remote Procedure Calls #

The Nakama Server allows developers to write custom logic and expose it to the client as RPCs.

Sagi-shi contains various logic that needs to be protected on the server, like checking if the player owns equipment before equipping it.

Creating server logic #

See the handling player equipment authoritatively recipe for an example of creating a remote procedure to check if the player owns equipment before equipping it.

Client RPCs #

Nakama Remote Procedures can be called from the client and take optional JSON payloads.

The Sagi-shi client makes an RPC to securely equip a hat:

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FOnRPC RpcSuccessDelegate;
RpcSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnRpcSuccess);

FOnError RpcErrorDelegate;
RpcErrorDelegate.AddDynamic(this, &ASagiShiActor::OnRpcError);

Client->RPC(Session, "EquipHat", "<PayloadString>", RpcSuccessDelegate, RpcErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnRpcSuccess(const FNakamaRPC& RPC)
{
	UE_LOG(LogTemp, Log, TEXT("New hat successfully equipped"));
}

void ASagiShiActor::OnRpcError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error reading storage objects: %s"), *Error.Message);
}

Friends #

Nakama Friends offers a complete social graph system to manage friendships amongst players.

Sagi-shi allows players to add friends, manage their relationships and play together.

Sagi-shi Friends screen
Friends screen

Adding friends #

Adding a friend in Nakama does not immediately add a mutual friend relationship. An outgoing friend request is created to each user, which they will need to accept.

Sagi-shi allows players to add friends by their usernames or user ids:

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auto successCallback = []()
{
    cout << "Successfully added friends" << endl;
};

auto errorCallback = [](const NError& error)
{
    cout << "Error adding friends " << error.message << endl;
};

TArray<FString> Ids = { "<SomeUserId>", "<AnotherUserId>" };
TArray<FString> Usernames = { "AlwaysTheImposter21", "SneakyBoi" };

FOnAddedFriend AddFriendsSuccessDelegate;
AddFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAddFriendsSuccess);

FOnError AddFriendsErrorDelegate;
AddFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddFriendsError);

Client->AddFriends(Session, Ids, Usernames, AddFriendsSuccessDelegate, AddFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnAddFriendsSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully added friends"));
}

void ASagiShiActor::OnAddFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Log, TEXT("Error adding friends: %s"), *Error.Message);
}

Friendship states #

Nakama friendships are categorized with the following states:

ValueState
0Mutual friends
1An outgoing friend request pending acceptance
2An incoming friend request pending acceptance
3Blocked by the user

Listing friends #

Nakama allows developers to list the player’s friends based on their friendship state.

Sagi-shi lists the 20 most recent mutual friends:

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int32 Limit = 20;
ENakamaFriendState FriendshipState = ENakamaFriendState::FRIEND;
FString Cursor = TEXT("");

FOnFriendsList GetFriendsSuccessDelegate;
GetFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsSuccess);

FOnError GetFriendsErrorDelegate;
GetFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddFriendsError);

Client->GetFriends(Session, Limit, FriendshipState, Cursor, GetFriendsSuccessDelegate, GetFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	UE_LOG(LogTemp, Log, TEXT("Friends:"));
	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("ID: %s"), *Friends.NakamaUsers[i].NakamaUser.Id);
	}
}

void ASagiShiActor::OnGetFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error retrieving friends: %s"), *Error.Message);
}

Accepting friend requests #

When accepting a friend request in Nakama the player adds a bi-directional friend relationship.

Nakama takes care of changing the state from pending to mutual for both.

In a complete game you would allow players to accept individual requests.

Sagi-shi just fetches and accepts all the incoming friend requests:

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int32 Limit = 1000;
ENakamaFriendState FriendshipState = ENakamaFriendState::INVITE_RECEIVED;
FString Cursor = TEXT("");

FOnFriendsList GetFriendsSuccessDelegate;
GetFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsSuccess);

FOnError GetFriendsErrorDelegate;
GetFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddFriendsError);

Client->GetFriends(Session, Limit, FriendshipState, Cursor, GetFriendsSuccessDelegate, GetFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
    // Subsequent delegate handlers omitted for brevity
		FOnAddedFriend OnAddFriendSuccessDelegate;
		FOnError OnAddFriendErrorDelegate;

		Client->AddFriends(Session, { Friends.NakamaUsers[i].NakamaUser.Id }, {}, OnAddFriendSuccessDelegate, OnAddFriendErrorDelegate);
	}
}

void ASagiShiActor::OnGetFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Log, TEXT("Error retrieving friends: %s"), *Error.Message);
}

Deleting friends #

Sagi-shi players can remove friends by their username or user id:

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FOnRemovedFriends RemoveFriendsSuccessDelegate;
RemoveFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnRemoveFriendsSuccess);

FOnError RemoveFriendsErrorDelegate;
RemoveFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnRemoveFriendsError);

// Delete friends by User ID
Client->RemoveFriends(Session, { "<SomeUserId>", "<AnotherUserId>" }, {}, RemoveFriendsSuccessDelegate, RemoveFriendsErrorDelegate);

// Delete friends by Username
Client->RemoveFriends(Session, {}, { "<SomeUsername>", "<AnotherUsername>" }, RemoveFriendsSuccessDelegate, RemoveFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnRemoveFriendsSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully deleted friends"));
}

void ASagiShiActor::OnRemoveFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error deleting friends: %s"), *Error.Message);
}

Blocking users #

Sagi-shi players can block others by their username or user id:

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FOnBlockedFriends BlockFriendsSuccessDelegate;
BlockFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnBlockedFriendsSuccess);

FOnError BlockFriendsErrorDelegate;
BlockFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnBlockedFriendsError);

// Block friends by User ID
Client->BlockFriends(Session, { "<SomeUserId>", "<AnotherUserId>" }, {}, BlockFriendsSuccessDelegate, BlockFriendsErrorDelegate);

// Block friends by Username
Client->BlockFriends(Session, {}, { "<SomeUsername>", "<AnotherUsername>" }, BlockFriendsSuccessDelegate, BlockFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnBlockedFriendsSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully blocked friends"));
}

void ASagiShiActor::OnBlockedFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error blocking friends: %s"), *Error.Message);
}

Status & Presence #

Nakama Status is a real-time status and presence service that allows users to set their online presence, update their status message and follow other user’s updates.

Players don’t have to be friends with others they want to follow.

Sagi-shi uses status messages and online presences to notify players when their friends are online and share matches.

Sagi-shi status update screen
Updating player status

Follow users #

The Nakama real-time APIs allow developers to subscribe to events on the socket, like a status presence change, and receive them in real-time.

The method to follow users also returns the current online users, known as presences, and their status.

Sagi-shi follows a player’s friends and notifies them when they are online:

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// Subscribe to the Status Presence event
FOnReceivedStatusPresence ReceivedStatusPresenceDelegate;
ReceivedStatusPresenceDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedStatusPresence);

RealtimeClient->PresenceStatusReceived = ReceivedStatusPresenceDelegate;
RealtimeClient->SetListenerStatusPresenceCallback();

// Get mutual friends
int32 Limit = 1000;
ENakamaFriendState FriendshipState = ENakamaFriendState::FRIEND;
FString Cursor = TEXT("");

FOnFriendsList GetFriendsSuccessDelegate;
GetFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsSuccess);

FOnError GetFriendsErrorDelegate;
GetFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddFriendsError);

Client->GetFriends(Session, Limit, FriendshipState, Cursor, GetFriendsSuccessDelegate, GetFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnReceivedStatusPresence(const FNakamaStatusPresenceEvent& UserPresenceData)
{
	for (int16 i = 0; i < UserPresenceData.Leaves.Num(); i++)
	{
		FNakamaUserPresence User = UserPresenceData.Leaves[i];
		UE_LOG(LogTemp, Log, TEXT("%s (%s) left status: %s"), *User.Username, *User.UserID, *User.Status);
	}

	for (int16 i = 0; i < UserPresenceData.Joins.Num(); i++)
	{
		FNakamaUserPresence User = UserPresenceData.Joins[i];
		UE_LOG(LogTemp, Log, TEXT("%s (%s) new status: %s"), *User.Username, *User.UserID, *User.Status);
	}
}

void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
		FOnFollowUsers FollowUsersSuccessDelegate;
		FollowUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnFollowUsersSuccess);

		FOnRtError FollowUsersErrorDelegate;
		FollowUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnFollowUsersError);

		RealtimeClient->FollowUsers({ Friends.NakamaUsers[i].NakamaUser.Id }, FollowUsersSuccessDelegate, FollowUsersErrorDelegate);
	}
}

void ASagiShiActor::OnGetFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error retrieving friends: %s"), *Error.Message);
}

void ASagiShiActor::OnFollowUsersSuccess(const FNakamaStatus& Status)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully followed users"));

	// Get the initial Status of any that are currently online.
	for (int16 i = 0; i < Status.Presences.Num(); i++)
	{
		FNakamaUserPresence User = Status.Presences[i];
		UE_LOG(LogTemp, Log, TEXT("%s (%s) current status: %s"), *User.Username, *User.UserID, *User.Status);
	}
}

void ASagiShiActor::OnFollowUsersError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error following users: %s"), *Error.Message);
}

Unfollow users #

Sagi-shi players can unfollow others:

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FOnUnFollowUsers UnfollowUsersSuccessDelegate;
UnfollowUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnUnfollowUsersSuccess);

FOnRtError UnfollowUsersErrorDelegate;
UnfollowUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnUnfollowUsersError);


RealtimeClient->UnFollowUsers({ "<UserId>" }, UnfollowUsersSuccessDelegate, UnfollowUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnUnfollowUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully unfollowed users"));
}

void ASagiShiActor::OnUnfollowUsersError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error unfollowing users: %s"), *Error.Message);
}

Updating player status #

Sagi-shi players can change and publish their status to their followers:

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FOnSetStatus SetStatusSuccessDelegate;
SetStatusSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnSetStatusSuccess);

FOnRtError SetStatusErrorDelegate;
SetStatusErrorDelegate.AddDynamic(this, &ASagiShiActor::OnSetStatusError);

RealtimeClient->UpdateStatus(TEXT("Viewing the Main Menu"), SetStatusSuccessDelegate, SetStatusErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnSetStatusSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully updated status"));
}

void ASagiShiActor::OnSetStatusError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error updating status: %s"), *Error.Message);
}

Groups #

Nakama Groups is a group or clan system with public/private visibility, user memberships and permissions, metadata and group chat.

Sagi-shi allows players to form and join groups to socialize and compete.

Sagi-shi groups screen
Groups list screen

Creating groups #

Groups have a public or private “open” visibility. Anyone can join public groups, but they must request to join and be accepted by a superadmin/admin of a private group.

Sagi-shi players can create groups around common interests:

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FString Name = TEXT("Imposters R Us");
FString Description = TEXT("A group for people who love playing the imposters.");
FString AvatarUrl = TEXT("");
FString LangTag = TEXT("");
bool bOpen = true;
int32 MaxSize = 100;

FOnCreateGroup CreateGroupSuccessDelegate;
CreateGroupSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnCreateGroupSuccess);

FOnError CreateGroupErrorDelegate;
CreateGroupErrorDelegate.AddDynamic(this, &ASagiShiActor::OnCreateGroupError);

Client->CreateGroup(Session, Name, Description, AvatarUrl, LangTag, bOpen, MaxSize, CreateGroupSuccessDelegate, CreateGroupErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnCreateGroupSuccess(FNakamaGroup Group)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully created group: %s"), *Group.Id);
}

void ASagiShiActor::OnCreateGroupError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error creating group: %s"), *Error.Message);
}

Update group visibility #

Nakama allows group superadmin or admin members to update some properties from the client, like the open visibility:

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FString GroupId = TEXT("<GroupId>");
FString Name = TEXT("New Name");
FString Description = TEXT("New description");
FString AvatarUrl = TEXT("");
FString LangTag = TEXT("");
bool bOpen = true;

FOnUpdateGroup UpdateGroupSuccessDelegate;
UpdateGroupSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnUpdateGroupSuccess);

FOnError UpdateGroupErrorDelegate;
UpdateGroupErrorDelegate.AddDynamic(this, &ASagiShiActor::OnUpdateGroupError);

Client->UpdateGroup(Session, GroupId, Name, Description, AvatarUrl, LangTag, bOpen, UpdateGroupSuccessDelegate, UpdateGroupErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnUpdateGroupSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully updated group"));
}

void ASagiShiActor::OnUpdateGroupError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error updating group: %s"), *Error.Message);
}

Update group size #

Other properties, like the group’s maximum member size, can only be changed on the server.

See the updating group size recipe for an example, and the Groups server function reference to learn more about updating groups on the server.

Sagi-shi group edit screen
Sagi-shi group edit

Listing and filtering groups #

Groups can be listed like other Nakama resources and also filtered with a wildcard group name.

Sagi-shi players use group listing and filtering to search for existing groups to join:

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FString GroupNameFilter = TEXT("imposter%");
int32 Limit = 20;
FString Cursor = TEXT("");

FOnGroupsList ListGroupsSuccessDelegate;
ListGroupsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupsSuccess);

FOnError ListGroupsErrorDelegate;
ListGroupsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupsError);

Client->ListGroups(Session, GroupNameFilter, Limit, Cursor, ListGroupsSuccessDelegate, ListGroupsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListGroupsSuccess(const FNakamaGroupList& Groups)
{
	for (int16 i = 0; i < Groups.Groups.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("%s: %s"), *Groups.Groups[i].Name, Groups.Groups[i].open ? TEXT("Public") : TEXT("Private"));
	}
}

void ASagiShiActor::OnListGroupsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing groups: %s"), *Error.Message);
}

Deleting groups #

Nakama allows group superadmins to delete groups.

Developers can disable this feature entirely, see the Guarding APIs guide for an example on how to protect various Nakama APIs.

Sagi-shi players can delete groups which they are superadmins for:

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FString GroupId = TEXT("<GroupId>");
FOnRemoveGroup DeleteGroupSuccessDelegate;
DeleteGroupSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteGroupSuccess);

FOnError DeleteGroupErrorDelegate;
DeleteGroupErrorDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteGroupError);

Client->DeleteGroup(Session, GroupId, DeleteGroupSuccessDelegate, DeleteGroupErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnDeleteGroupSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully deleted group"));
}

void ASagiShiActor::OnDeleteGroupError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error deleting groups: %s"), *Error.Message);
}

Group metadata #

Like Users Accounts, Groups can have public metadata.

Sagi-shi uses group metadata to store the group’s interests, active player times and languages spoken.

Group metadata can only be updated on the server. See the updating group metadata recipe for an example.

The Sagi-shi client makes an RPC with the group metadata payload:

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/* Define a metadata struct */
USTRUCT()
struct FGroupMetadata
{
	GENERATED_BODY()

public:
	UPROPERTY()
	TArray<FString> Interests;

	UPROPERTY()
	TArray<FString> ActiveTimes;

	UPROPERTY()
	TArray<FString> Languages;
};

FString GroupId = TEXT("<GroupId>");
FGroupMetadata GroupMetadata;
GroupMetadata.Interests = { "Deception", "Sabotage", "Cute Furry Bunnies" };
GroupMetadata.ActiveTimes = { "9am-2pm Weekdays", "9am-10am Weekends" };
GroupMetadata.Languages = { "English", "German" };

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(GroupMetadata, Json);

FOnRPC RpcSuccessDelegate;
RpcSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnRpcSuccess);

FOnError RpcErrorDelegate;
RpcErrorDelegate.AddDynamic(this, &ASagiShiActor::OnRpcError);

Client->RPC(Session, TEXT("UpdateGroupMetadata"), Json, RpcSuccessDelegate, RpcErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnRpcSuccess(const FNakamaRPC& RPC)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully updated group metadata"));
}

void ASagiShiActor::OnRpcError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error updating group metadata: %s"), *Error.Message);
}

Group membership states #

Nakama group memberships are categorized with the following states:

CodePurpose
0SuperadminThere must at least be 1 superadmin in any group. The superadmin has all the privileges of the admin and can additionally delete the group and promote admin members.
1AdminThere can be one of more admins. Admins can update groups as well as accept, kick, promote, demote, ban or add members.
2MemberRegular group member. They cannot accept join requests from new users.
3Join requestA new join request from a new user. This does not count towards the maximum group member count.

Joining a group #

If a player joins a public group they immediately become a member, but if they try and join a private group they must be accepted by a group admin.

Sagi-shi players can join a group:

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FString GroupId = TEXT("<GroupId>");

FOnJoinedGroup JoinGroupSuccessDelegate;
JoinGroupSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinGroupSuccess);

FOnError JoinGroupErrorDelegate;
JoinGroupErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinGroupError);

Client->JoinGroup(Session, GroupId, JoinGroupSuccessDelegate, JoinGroupErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinGroupSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined group"));
}

void ASagiShiActor::OnJoinGroupError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error joining group: %s"), *Error.Message);
}

Listing the user’s groups #

Sagi-shi players can list groups they are a member of:

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int32 Limit = 100;
ENakamaGroupState State = ENakamaGroupState::MEMBER;
FString Cursor = TEXT("");

FOnUserGroups ListUserGroupsSuccessDelegate;
ListUserGroupsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListUserGroupsSuccess);

FOnError ListUserGroupsErrorDelegate;
ListUserGroupsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListUserGroupsError);

Client->ListUserGroups(Session, Session->SessionData.UserId, Limit, State, Cursor, ListUserGroupsSuccessDelegate, ListUserGroupsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListUserGroupsSuccess(const FNakamaUserGroupList& UserGroups)
{
	for (int16 i = 0; i < UserGroups.UserGroups.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("%s"), *UserGroups.UserGroups[i].Group.Name);
	}
}

void ASagiShiActor::OnListUserGroupsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing user groups: %s"), *Error.Message);
}

Listing members #

Sagi-shi players can list a group’s members:

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FString GroupId = TEXT("<GroupId>");
int32 Limit = 100;
ENakamaGroupState State = ENakamaGroupState::MEMBER;
FString Cursor = TEXT("");

FOnListGroupMembers ListGroupUsersSuccessDelegate;
ListGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupUsersSuccess);

FOnError ListGroupUsersErrorDelegate;
ListGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupUsersError);

Client->ListGroupUsers(Session, GroupId, Limit, State, Cursor, ListGroupUsersSuccessDelegate, ListGroupUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListGroupUsersSuccess(const FNakamaGroupUsersList& GroupUsers)
{
	for (int16 i = 0; i < GroupUsers.GroupUsers.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("%s"), *GroupUsers.GroupUsers[i].User.Username);
	}
}

void ASagiShiActor::OnListGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing group users: %s"), *Error.Message);
}

Accepting join requests #

Private group admins or superadmins can accept join requests by re-adding the user to the group.

Sagi-shi first lists all the users with a join request state and then loops over and adds them to the group:

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FString GroupId = TEXT("<GroupId>");
int32 Limit = 100;
ENakamaGroupState State = ENakamaGroupState::JOIN_REQUEST;
FString Cursor = TEXT("");

FOnListGroupMembers ListGroupUsersSuccessDelegate;
ListGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupUsersSuccess);

FOnError ListGroupUsersErrorDelegate;
ListGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListGroupUsersError);

Client->ListGroupUsers(Session, GroupId, Limit, State, Cursor, ListGroupUsersSuccessDelegate, ListGroupUsersErrorDelegate);

void ASagiShiActor::OnListGroupUsersSuccess(const FNakamaGroupUsersList& GroupUsers)
{
	for (int16 i = 0; i < GroupUsers.GroupUsers.Num(); i++)
	{
		FOnAddGroupUsers AddGroupUsersSuccessDelegate;
		AddGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAddGroupUsersSuccess);

		FOnError AddGroupUsersErrorDelegate;
		AddGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddGroupUsersError);

		Client->AddGroupUsers(Session, TEXT("<GroupId>"), {GroupUsers.GroupUsers[i].User.Id}, AddGroupUsersSuccessDelegate, AddGroupUsersErrorDelegate);
		UE_LOG(LogTemp, Log, TEXT("%s"), *GroupUsers.GroupUsers[i].User.Username);
	}
}

void ASagiShiActor::OnListGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing group users: %s"), *Error.Message);
}

void ASagiShiActor::OnAddGroupUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully added group users"));
}

void ASagiShiActor::OnAddGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error adding group users: %s"), *Error.Message);
}

Promoting members #

Nakama group members can be promoted to admin or superadmin roles to help manage a growing group or take over if members leave.

Admins can promote other members to admins, and superadmins can promote other members up to superadmins.

The members will be promoted up one level. For example:

  • Promoting a member will make them an admin
  • Promoting an admin will make them a superadmin
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FString GroupId = TEXT("<GroupId>");

FOnPromoteGroupUsers PromoteGroupUsersSuccessDelegate;
PromoteGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnPromoteGroupUsersSuccess);

FOnError PromoteGroupUsersErrorDelegate;
PromoteGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnPromoteGroupUsersError);

Client->PromoteGroupUsers(Session, GroupId, { TEXT("<UserId>") }, PromoteGroupUsersSuccessDelegate, PromoteGroupUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnPromoteGroupUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully promoted group users"));
}

void ASagiShiActor::OnPromoteGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error promoting group users: %s"), *Error.Message);
}

Demoting members #

Sagi-shi group admins and superadmins can demote members:

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FString GroupId = TEXT("<GroupId>");

FOnDemoteGroupUsers DemoteGroupUsersSuccessDelegate;
DemoteGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnDemoteGroupUsersSuccess);

FOnError DemoteGroupUsersErrorDelegate;
DemoteGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnDemoteGroupUsersError);

Client->DemoteGroupUsers(Session, GroupId, { TEXT("<UserId>") }, DemoteGroupUsersSuccessDelegate, DemoteGroupUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnDemoteGroupUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully demoted group users"));
}

void ASagiShiActor::OnDemoteGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error demoting group users: %s"), *Error.Message);
}

Kicking members #

Sagi-shi group admins and superadmins can remove group members:

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FString GroupId = TEXT("<GroupId>");

FOnKickGroupUsers KickGroupUsersSuccessDelegate;
KickGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnKickGroupUsersSuccess);

FOnError KickGroupUsersErrorDelegate;
KickGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnKickGroupUsersError);

Client->KickGroupUsers(Session, GroupId, { TEXT("<UserId>") }, KickGroupUsersSuccessDelegate, KickGroupUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnKickGroupUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully kicked group users"));
}

void ASagiShiActor::OnKickGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error kicking group users: %s"), *Error.Message);
}

Banning members #

Sagi-shi group admins and superadmins can ban a user when demoting or kicking is not severe enough:

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FString GroupId = TEXT("<GroupId>");

FOnBanGroupUsers BanGroupUsersSuccessDelegate;
BanGroupUsersSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnBanGroupUsersSuccess);

FOnError BanGroupUsersErrorDelegate;
BanGroupUsersErrorDelegate.AddDynamic(this, &ASagiShiActor::OnBanGroupUsersError);

Client->BanGroupUsers(Session, GroupId, { TEXT("<UserId>") }, BanGroupUsersSuccessDelegate, BanGroupUsersErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnBanGroupUsersSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully banned group users"));
}

void ASagiShiActor::OnBanGroupUsersError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error banning group users: %s"), *Error.Message);
}

Leaving groups #

Sagi-shi players can leave a group:

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FString GroupId = TEXT("<GroupId>");

FOnLeaveGroup LeaveGroupSuccessDelegate;
LeaveGroupSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnLeaveGroupSuccess);

FOnError LeaveGroupErrorDelegate;
LeaveGroupErrorDelegate.AddDynamic(this, &ASagiShiActor::OnLeaveGroupError);

Client->LeaveGroup(Session, GroupId, LeaveGroupSuccessDelegate, LeaveGroupErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnLeaveGroupSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully left group"));
}

void ASagiShiActor::OnLeaveGroupError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error leaving group: %s"), *Error.Message);
}

Chat #

Nakama Chat is a real-time chat system for groups, private/direct messages and dynamic chat rooms.

Sagi-shi uses dynamic chat during matches, for players to mislead each other and discuss who the imposters are, group chat and private/direct messages.

Sagi-shi chat screen
Sagi-shi Chat

Joining dynamic rooms #

Sagi-shi matches have a non-persistent chat room for players to communicate in:

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FString RoomName = TEXT("<MatchId>");
bool Persistence = false;
bool Hidden = false;

FOnJoinChat JoinChatSuccessDelegate;
JoinChatSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatSuccess);

FOnRtError JoinChatErrorDelegate;
JoinChatErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatError);

RealtimeClient->JoinChat(RoomName, ENakamaChannelType::ROOM, Persistence, Hidden, JoinChatSuccessDelegate, JoinChatErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinChatSuccess(FNakamaChannel Channel)
{
	UE_LOG(LogTemp, Log, TEXT("Connected to channel: %s"), *Channel.Id);
}

void ASagiShiActor::OnJoinChatError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error connecting to channel: %s"), *Error.Message);
}

Joining group chat #

Sagi-shi group members can have conversations that span play sessions in a persistent group chat channel:

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FString GroupId = TEXT("<GroupId>");
bool Persistence = false;
bool Hidden = false;

FOnJoinChat JoinChatSuccessDelegate;
JoinChatSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatSuccess);

FOnRtError JoinChatErrorDelegate;
JoinChatErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatError);

RealtimeClient->JoinChat(GroupId, ENakamaChannelType::GROUP, Persistence, Hidden, JoinChatSuccessDelegate, JoinChatErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinChatSuccess(FNakamaChannel Channel)
{
	UE_LOG(LogTemp, Log, TEXT("Connected to channel: %s"), *Channel.Id);
}

void ASagiShiActor::OnJoinChatError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error connecting to channel: %s"), *Error.Message);
}

Joining direct chat #

Sagi-shi players can also chat privately one-to-one during or after matches and view past messages:

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FString UserId = TEXT("<UserId>");
bool Persistence = true;
bool Hidden = false;

FOnJoinChat JoinChatSuccessDelegate;
JoinChatSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatSuccess);

FOnRtError JoinChatErrorDelegate;
JoinChatErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinChatError);

RealtimeClient->JoinChat(UserId, ENakamaChannelType::DIRECT_MESSAGE, Persistence, Hidden, JoinChatSuccessDelegate, JoinChatErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinChatSuccess(FNakamaChannel Channel)
{
	UE_LOG(LogTemp, Log, TEXT("Connected to channel: %s"), *Channel.Id);
}

void ASagiShiActor::OnJoinChatError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error connecting to channel: %s"), *Error.Message);
}

Sending messages #

Sending messages is the same for every type of chat channel. Messages contain chat text and emotes and are sent as JSON serialized data:

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USTRUCT()
struct FChatMessage
{
	GENERATED_BODY()

public:
	UPROPERTY()
	FString Message;

	UPROPERTY()
	FString Emote;

	UPROPERTY()
	FString EmoteTarget;

  UPROPERTY()
  FString MatchId;

  UPROPERTY()
  FString PartyId;
};

FString ChannelId = TEXT("<ChannelId>");

FOnWriteChatMessage SendMessageSuccessDelegate;
SendMessageSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageSuccess);

FOnRtError SendMessageErrorDelegate;
SendMessageErrorDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageError);

FChatMessage ChatMessage;
ChatMessage.Message = TEXT("I think Red is the imposter!");

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(ChatMessage, Json);

RealtimeClient->SendMessage(ChannelId, Json, SendMessageSuccessDelegate, SendMessageErrorDelegate);

FChatMessage ChatMessage2;
ChatMessage2.Emote = TEXT("point");
ChatMessage2.EmoteTarget = TEXT("<RedPlayerUserId");

FString Json2;
FJsonObjectConverter::UStructToJsonObjectString(ChatMessage2, Json2);

RealtimeClient->SendMessage(ChannelId, Json2, SendMessageSuccessDelegate, SendMessageErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnSendMessageSuccess(FNakamaChannelMessageAck ChannelMessage)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully sent message: %s"), *ChannelMessage.MessageId);
}

void ASagiShiActor::OnSendMessageError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error sending message: %s"), *Error.Message);
}

Listing message history #

Message listing takes a parameter which indicates if messages are received from oldest to newest (forward) or newest to oldest.

Sagi-shi players can list a group’s message history:

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FString ChannelId = TEXT("<ChannelId>");
int32 Limit = 100;
bool Forward = false;
FString Cursor = TEXT("");

FOnListChannelMessages ListChannelMessagesSuccessDelegate;
ListChannelMessagesSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListChannelMessagesSuccess);

FOnError ListChannelMessagesErrorDelegate;
ListChannelMessagesErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListChannelMessagesError);

Client->ListChannelMessages(Session, ChannelId, Limit, Cursor, Forward, ListChannelMessagesSuccessDelegate, ListChannelMessagesErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListChannelMessagesSuccess(const FNakamaChannelMessageList& MessageList)
{
	for (int16 i = 0; i < MessageList.Messages.Num(); i++)
	{
		UE_LOG(LogTemp, Log, TEXT("%s: %s"), *MessageList.Messages[i].Username, *MessageList.Messages[i].Content);
	}
}

void ASagiShiActor::OnListChannelMessagesError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error retrieving messages: %s"), *Error.Message);
}

Chat also has cacheable cursors to fetch the most recent messages. Read more about cacheable cursors in the listing notifications documentation.

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FString Cursor = MessageList.NextCursor;
Client->ListChannelMessages(Session, ChannelId, Limit, Cursor, Forward, ListChannelMessagesSuccessDelegate, ListChannelMessagesErrorDelegate);

Matches #

Nakama supports Server Authoritative and Server Relayed multiplayer matches.

In server authoritative matches the server controls the gameplay loop and must keep all clients up to date with the current state of the game.

In server relayed matches the client is in control, with the server only relaying information to the other connected clients.

In a competitive game such as Sagi-shi, server authoritative matches would likely be used to prevent clients from interacting with your game in unauthorized ways.

For the simplicity of this guide, the server relayed model is used.

Creating matches #

Sagi-shi players can create their own matches and invite their online friends to join:

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FOnCreateMatch CreateMatchSuccessDelegate;
CreateMatchSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnCreateMatchSuccess);

FOnRtError CreateMatchErrorDelegate;
CreateMatchErrorDelegate.AddDynamic(this, &ASagiShiActor::OnCreateMatchError);

RealtimeClient->CreateMatch(CreateMatchSuccessDelegate, CreateMatchErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnCreateMatchSuccess(FNakamaMatch Match)
{
	CurrentMatch = Match;

	UE_LOG(LogTemp, Log, TEXT("Created match: %s"), *Match.MatchId);

	// Get the users friends so we can send them invites to the match
	FOnFriendsList GetFriendsSuccessDelegate;
	GetFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsSuccess);

	FOnError GetFriendsErrorDelegate;
	GetFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsError);

	Client->GetFriends(Session, 100, ENakamaFriendState::FRIEND, TEXT(""), GetFriendsSuccessDelegate, GetFriendsErrorDelegate);
}

void ASagiShiActor::OnCreateMatchError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error creating match: %s"), *Error.Message);
}

void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
		FOnWriteChatMessage SendDirectMessageSuccessDelegate;
		SendDirectMessageSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageSuccess);

		FOnRtError SendDirectMessageErrorDelegate;
		SendDirectMessageErrorDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageError);

		FChatMessage ChatMessage;
		ChatMessage.Message = FString::Printf(TEXT("Hey %s, join me for a match!"), *Friends.NakamaUsers[i].NakamaUser.Username);
		ChatMessage.MatchId = CurrentMatch.MatchId;

		FString Json;
		FJsonObjectConverter::UStructToJsonObjectString(ChatMessage, Json);

		RealtimeClient->SendDirectMessage(Friends.NakamaUsers[i].NakamaUser.Id, Json, SendDirectMessageSuccessDelegate, SendDirectMessageErrorDelegate);
	}
}

void ASagiShiActor::OnGetFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Log, TEXT("Error retrieving friends: %s"), *Error.Message);
}

Joining matches #

Sagi-shi players can try to join existing matches if they know the id:

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FString MatchId = "<MatchId>";
TMap<FString, FString> Metadata = {
  { "Region", "EU" }
};

FOnCreateMatch JoinMatchSuccessDelegate;
JoinMatchSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinMatchSuccess);

FOnRtError JoinMatchErrorDelegate;
JoinMatchErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinMatchError);

RealtimeClient->JoinMatch(MatchId, Metadata, JoinMatchSuccessDelegate, JoinMatchErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinMatchSuccess(FNakamaMatch Match)
{
	CurrentMatch = Match;
	UE_LOG(LogTemp, Log, TEXT("Successfully joined match: %s"), *Match.MatchId);
}

void ASagiShiActor::OnJoinMatchError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error joining match: %s"), *Error.Message);
}

Or set up a real-time matchmaker listener and add themselves to the matchmaker:

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FOnReceivedMatchmakerMatched MatchmakerMatchedSuccessDelegate;
MatchmakerMatchedSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnMatchmakerMatchedSuccess);

RealtimeClient->MatchmakerMatchMatched = MatchmakerMatchedSuccessDelegate;
RealtimeClient->SetListenerMatchmakerMatchedCallback();

int32 MinPlayers = 2;
int32 MaxPlayers = 10;
FString Query = TEXT("");
TMap<FString, FString> StringProperties;
TMap<FString, int32> NumericProperties;
int32 CountMultiple = 0;
bool IgnoreCountMultiple = true;

FOnMatchmakerTicket AddMatchmakerSuccessDelegate;
AddMatchmakerSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerSuccess);

FOnRtError AddMatchmakerErrorDelegate;
AddMatchmakerErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerError);

RealtimeClient->AddMatchmaker(MinPlayers, MaxPlayers, Query, StringProperties, NumericProperties, CountMultiple, IgnoreCountMultiple, AddMatchmakerSuccessDelegate, AddMatchmakerErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnAddMatchmakerSuccess(FString Ticket)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined matchmaker: %s"), *Ticket);
}

void ASagiShiActor::OnAddMatchmakerError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error adding matchmaker: %s"), *Error.Message);
}

void ASagiShiActor::OnMatchmakerMatchedSuccess(const FNakamaMatchmakerMatched& Match)
{
	TMap<FString, FString> Metadata;
	FOnCreateMatch JoinMatchSuccessDelegate;
	FOnRtError JoinMatchErrorDelegate;

	RealtimeClient->JoinMatch(Match.MatchId, Metadata, JoinMatchSuccessDelegate, JoinMatchErrorDelegate);
}

Joining matches from player status

Sagi-shi players can update their status when they join a new match:

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USTRUCT()
struct FUserStatus
{
	GENERATED_BODY()

public:
	UPROPERTY()
	FString Status;
	
	UPROPERTY()
	FString MatchId;
};

FUserStatus UserStatus;
UserStatus.Status = TEXT("Playing a match");
UserStatus.MatchId = TEXT("<MatchId>");

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(UserStatus, Json);

FOnSetStatus UpdateStatusSuccessDelegate;
FOnRtError UpdateStatusErrorDelegate;

RealtimeClient->UpdateStatus(Json, UpdateStatusSuccessDelegate, UpdateStatusErrorDelegate);

When their followers receive the real-time status event they can try and join the match:

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void ASagiShiActor::OnReceivedStatusPresence(const FNakamaStatusPresenceEvent& UserPresenceData)
{
	for (int16 i = 0; i < UserPresenceData.Joins.Num(); i++)
	{
		FNakamaUserPresence User = UserPresenceData.Joins[i];

		FUserStatus UserStatus;
		FJsonObjectConverter::JsonObjectStringToUStruct(User.Status, &UserStatus);

		if (UserStatus.MatchId != "")
		{
			FOnCreateMatch JoinMatchSuccessDelegate;
			FOnRtError JoinMatchErrorDelegate;

			RealtimeClient->JoinMatch(UserStatus.MatchId, {}, JoinMatchSuccessDelegate, JoinMatchErrorDelegate);
		}
	}
}

Listing matches #

Match Listing takes a number of criteria to filter matches by including player count, a match label and an option to provide a more complex search query.

Sagi-shi matches start in a lobby state. The match exists on the server but the actual gameplay doesn’t start until enough players have joined.

Sagi-shi can then list matches that are waiting for more players:

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int32 MinPlayers = 2;
int32 MaxPlayers = 10;
int32 Limit = 10;
bool Authoritative = true;
FString Label = TEXT("");

FOnMatchlist ListMatchesSuccessDelegate;
ListMatchesSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListMatchesSuccess);

FOnError ListMatchesErrorDelegate;
ListMatchesErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListMatchesError);

Client->ListMatches(Session, MinPlayers, MaxPlayers, Limit, Label, Authoritative, ListMatchesSuccessDelegate, ListMatchesErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListMatchesSuccess(const FNakamaMatchList& MatchList)
{
	for (int16 i = 0; i < MatchList.Matches.Num(); i++)
	{
		FNakamaMatch Match = MatchList.Matches[i];
		UE_LOG(LogTemp, Log, TEXT("%s:%d/10 players"), *Match.MatchId, Match.Size);
	}
}

void ASagiShiActor::OnListMatchesError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing matches: %s"), *Error.Message);
}

To find a match that has a label of "AnExactMatchLabel":

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FString Label = TEXT("AnExactMatchLabel");

Spawning players #

The match object has a list of current online users, known as presences.

Sagi-shi uses the match presences to spawn players on the client:

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// Assuming an FGameObject struct

TMap<FString, FGameObject> Players;
for (int16 i = 0; i < Match.Presences.Num(); i++)
{
  FNakamaUserPresence Presence = Presences[i];
  FGameObject GameObject = SpawnPlayer(); // Instantiate player object
  Players.Add(Presence.SessionID, GameObject);
}

Sagi-shi keeps the spawned players up-to-date as they leave and join the match using the match presence received event:

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FOnReceivedMatchPresenceCallback ReceivedMatchPresenceDelegate;
ReceivedMatchPresenceDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedMatchPresence);

RealtimeClient->MatchmakerPresenceCallback = ReceivedMatchPresenceDelegate;
RealtimeClient->SetListenerMatchPresenceCallback();

/* Delegate handlers */

void ASagiShiActor::OnReceivedMatchPresence(const FNakamaMatchPresenceEvent& PresenceEvent)
{
	for (int16 i = 0; i < PresenceEvent.Joins.Num(); i++)
	{
		FNakamaUserPresence Presence = PresenceEvent.Joins[i];
		FGameObject GameObject = SpawnPlayer(); // Instantiate player object
		Players.Add(Presence.SessionID, GameObject);
	}

	for (int16 i = 0; i < PresenceEvent.Leaves.Num(); i++)
	{
		FNakamaUserPresence Presence = PresenceEvent.Leaves[i];
		if (Players.Contains(Presence.SessionID))
		{
			Players.Remove(Presence.SessionID);
		}
	}
}

Sending match state #

Nakama has real-time networking to send and receive match state as players move and interact with the game world.

During the match, each Sagi-shi client sends match state to the server to be relayed to the other clients.

Match state contains an op code that lets the receiver know what data is being received so they can deserialize it and update their view of the game.

Example op codes used in Sagi-shi:

  • 1: player position
  • 2: player calling vote

Sending player position

Define a class to represent Sagi-shi player position states:

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USTRUCT()
struct FPositionState
{
	GENERATED_BODY()

public:
	UPROPERTY()
	float X;

	UPROPERTY()
	float Y;

	UPROPERTY()
	float Z;
};

Create an instance from the player’s transform, set the op code and send the JSON encoded state:

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// Assuming a Position variable
FPositionState PositionState;
PositionState.X = Position.X;
PositionState.Y = Position.Y;
PositionState.Z = Position.Z;

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(PositionState, Json);

int64 OpCode = 1;
RealtimeClient->SendMatchData(CurrentMatch.MatchId, OpCode, Json, {});

Op Codes as a static class

Sagi-shi has many networked game actions. Using defines for op codes will keep your code easier to follow and maintain:

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#define OPCODE_POSITION 1
#define OPCODE_VOTE 1

// ...

RealtimeClient->SendMatchData(CurrentMatch.MatchId, OPCODE_POSITION, Json, {});

Receiving match state #

Sagi-shi players can receive match data from the other connected clients by subscribing to the match state received event:

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FOnReceivedMatchData ReceivedMatchDataDelegate;
ReceivedMatchDataDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedMatchData);

RealtimeClient->MatchDataCallback = ReceivedMatchDataDelegate;
RealtimeClient->SetListenerMatchDataCallback();

/* Delegate handlers */

void ASagiShiActor::OnReceivedMatchData(const FNakamaMatchData& MatchData)
{
	switch (MatchData.OpCode)
	{
	case OPCODE_POSITION:
		FPositionState PositionState;
		FJsonObjectConverter::JsonObjectStringToUStruct(MatchData.Data, &PositionState);

		// Update the GameObject associated with that player.
		if (Players.Contains(MatchData.Presence.SessionID))
		{
			// Here we would normally do something like smoothly interpolate to the new position, but for this example let's just set the position directly.
			FVector NewPosition = FVector(PositionState.X, PositionState.Y, PositionState.Z);
			Players[MatchData.Presence.SessionID].Position = NewPosition;
		}
		break;
	default:
		UE_LOG(LogTemp, Error, TEXT("Unsupported opcode"));
		break;
	}
}

Matchmaker #

Developers can find matches for players using Match Listing or the Nakama Matchmaker, which enables players join the real-time matchmaking pool and be notified when they are matched with other players that match their specified criteria.

Matchmaking helps players find each other, it does not create a match. This decoupling is by design, allowing you to use matchmaking for more than finding a game match. For example, if you were building a social experience you could use matchmaking to find others to chat with.

Add matchmaker #

Matchmaking criteria can be simple, find 2 players, or more complex, find 2-10 players with a minimum skill level interested in a specific game mode.

Sagi-shi allows players to join the matchmaking pool and have the server match them with other players:

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FOnReceivedMatchmakerMatched MatchmakerMatchedSuccessDelegate;
MatchmakerMatchedSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnMatchmakerMatchedSuccess);

RealtimeClient->MatchmakerMatchMatched = MatchmakerMatchedSuccessDelegate;
RealtimeClient->SetListenerMatchmakerMatchedCallback();

int32 MinPlayers = 2;
int32 MaxPlayers = 10;
FString Query = TEXT("+skill:>100 mode:sabotage");
TMap<FString, FString> StringProperties = { { "mode", "sabotage" } };
TMap<FString, int32> NumericProperties = { { "skill", 125 }};
int32 CountMultiple = 0;
bool IgnoreCountMultiple = true;

FOnMatchmakerTicket AddMatchmakerSuccessDelegate;
AddMatchmakerSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerSuccess);

FOnRtError AddMatchmakerErrorDelegate;
AddMatchmakerErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerError);

RealtimeClient->AddMatchmaker(MinPlayers, MaxPlayers, Query, StringProperties, NumericProperties, CountMultiple, IgnoreCountMultiple, AddMatchmakerSuccessDelegate, AddMatchmakerErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnAddMatchmakerSuccess(FString Ticket)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined matchmaker: %s"), *Ticket);
}

void ASagiShiActor::OnAddMatchmakerError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error adding matchmaker: %s"), *Error.Message);
}

void ASagiShiActor::OnMatchmakerMatchedSuccess(const FNakamaMatchmakerMatched& Match)
{
	TMap<FString, FString> Metadata;
	FOnCreateMatch JoinMatchSuccessDelegate;
	FOnRtError JoinMatchErrorDelegate;

	RealtimeClient->JoinMatch(Match.MatchId, Metadata, JoinMatchSuccessDelegate, JoinMatchErrorDelegate);
}

Parties #

Nakama Parties is a real-time system that allows players to form short lived parties that don’t persist after all players have disconnected.

Sagi-shi allows friends to form a party and matchmake together.

Creating parties #

The player who creates the party is the party’s leader. Parties have maximum number of players and can be open to automatically accept players or closed so that the party leader can accept incoming join requests.

Sagi-shi uses closed parties with a maximum of 4 players:

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bool Open = false;
int32 MaxPlayers = 4;

FOnCreateParty CreatePartySuccessDelegate;
CreatePartySuccessDelegate.AddDynamic(this, &ASagiShiActor::OnCreatePartySuccess);

FOnRtError CreatePartyErrorDelegate;
CreatePartyErrorDelegate.AddDynamic(this, &ASagiShiActor::OnCreatePartyError);

RealtimeClient->CreateParty(Open, MaxPlayers, CreatePartySuccessDelegate, CreatePartyErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnCreatePartySuccess(FNakamaParty Party)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully created party: %s"), *Party.Id);
}

void ASagiShiActor::OnCreatePartyError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error creating party: %s"), *Error.Message);
}

Sagi-shi shares party ids with friends via private/direct messages:

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// Get the users friends so we can send them invites to the party
FOnFriendsList GetFriendsSuccessDelegate;
GetFriendsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsSuccess);

FOnError GetFriendsErrorDelegate;
GetFriendsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnGetFriendsError);

Client->GetFriends(Session, 100, ENakamaFriendState::FRIEND, TEXT(""), GetFriendsSuccessDelegate, GetFriendsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
		FOnWriteChatMessage SendDirectMessageSuccessDelegate;
		SendDirectMessageSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageSuccess);

		FOnRtError SendDirectMessageErrorDelegate;
		SendDirectMessageErrorDelegate.AddDynamic(this, &ASagiShiActor::OnSendMessageError);

		FChatMessage ChatMessage;
		ChatMessage.Message = FString::Printf(TEXT("Hey %s, wanna join the party?"), *Friends.NakamaUsers[i].NakamaUser.Username);
		ChatMessage.PartyId = CurrentParty.PartyId;

		FString Json;
		FJsonObjectConverter::UStructToJsonObjectString(ChatMessage, Json);

		RealtimeClient->SendDirectMessage(Friends.NakamaUsers[i].NakamaUser.Id, Json, SendDirectMessageSuccessDelegate, SendDirectMessageErrorDelegate);
	}
}

void ASagiShiActor::OnGetFriendsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Log, TEXT("Error retrieving friends: %s"), *Error.Message);
}

Joining parties #

Safi-shi players can join parties from chat messages by checking for the party id in the message:

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FOnReceivedChannelMessage ReceivedChannelMessageDelegate;
ReceivedChannelMessageDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedChannelMessage);

RealtimeClient->ChannelMessageReceived = ReceivedChannelMessageDelegate;
RealtimeClient->SetListenerChannelMessageCallback();

/* Delegate handlers */

void ASagiShiActor::OnReceivedChannelMessage(const FNakamaChannelMessage& ChannelMessage)
{
	FChatMessage ChatMessage;
	FJsonObjectConverter::JsonObjectStringToUStruct(ChannelMessage.Content, &ChatMessage);

	if (ChatMessage.PartyId != "")
	{
		FOnJoinParty JoinPartySuccessDelegate;
		JoinPartySuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinPartySuccess);

		FOnRtError JoinPartyErrorDelegate;
		JoinPartyErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinPartyError);

		RealtimeClient->JoinParty(ChatMessage.PartyId, JoinPartySuccessDelegate, JoinPartyErrorDelegate);
	}
}

void ASagiShiActor::OnJoinPartySuccess(FString PartyId)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined party: %s"), *PartyId);
}

void ASagiShiActor::OnJoinPartyError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error joining party: %s"), *Error.Message);
}

Promoting a member #

Sagi-shi party members can be promoted to the party leader:

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FOnPromotePartyMember PromotePartyMemberSuccessDelegate;
PromotePartyMemberSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnPromotePartyMemberSuccess);

FOnRtError PromotePartyMemberErrorDelegate;
PromotePartyMemberErrorDelegate.AddDynamic(this, &ASagiShiActor::OnPromotePartyMemberError);

for (int16 i = 0; i < Party.Presences.Num(); i++)
{
  RealtimeClient->PromotePartyMember(Party.Id, Party.Presences[i], PromotePartyMemberSuccessDelegate, PromotePartyMemberErrorDelegate);
}

/* Delegate handlers */

void ASagiShiActor::OnPromotePartyMemberSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully promoted party member"));
}

void ASagiShiActor::OnPromotePartyMemberError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error promoting party member: %s"), *Error.Message);
}

Leaving parties #

Sagi-shi players can leave parties:

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FOnLeaveParty LeavePartySuccessDelegate;
LeavePartySuccessDelegate.AddDynamic(this, &ASagiShiActor::OnLeavePartySuccess);

FOnRtError LeavePartyErrorDelegate;
LeavePartyErrorDelegate.AddDynamic(this, &ASagiShiActor::OnLeavePartyError);

RealtimeClient->LeaveParty(Party.Id, LeavePartySuccessDelegate, LeavePartyErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnLeavePartySuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully left party"));
}

void ASagiShiActor::OnLeavePartyError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error leaving party: %s"), *Error.Message);
}

Matchmaking with parties #

One of the main benefits of joining a party is that all the players can join the matchmaking pool together.

Sagi-shi players can listen to the the matchmaker matched event and join the match when one is found:

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FOnReceivedMatchmakerMatched MatchmakerMatchedSuccessDelegate;
MatchmakerMatchedSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnMatchmakerMatchedSuccess);

RealtimeClient->MatchmakerMatchMatched = MatchmakerMatchedSuccessDelegate;
RealtimeClient->SetListenerMatchmakerMatchedCallback();

/* Delegate handlers */

void ASagiShiActor::OnMatchmakerMatchedSuccess(const FNakamaMatchmakerMatched& Match)
{
	TMap<FString, FString> Metadata;
	FOnCreateMatch JoinMatchSuccessDelegate;
	FOnRtError JoinMatchErrorDelegate;

	RealtimeClient->JoinMatch(Match.MatchId, Metadata, JoinMatchSuccessDelegate, JoinMatchErrorDelegate);
}

The party leader will start the matchmaking for their party:

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int32 MinPlayers = 2;
int32 MaxPlayers = 10;
FString Query = TEXT("");
TMap<FString, FString> StringProperties;
TMap<FString, int32> NumericProperties;
int32 CountMultiple = 0;
bool IgnoreCountMultiple = true;

FOnAddMatchmakerParty AddMatchmakerPartySuccessDelegate;
AddMatchmakerPartySuccessDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerPartySuccess);

FOnRtError AddMatchmakerPartyErrorDelegate;
AddMatchmakerPartyErrorDelegate.AddDynamic(this, &ASagiShiActor::OnAddMatchmakerPartyError);

RealtimeClient->AddMatchmakerParty(Party.Id, Query, MinPlayers, MaxPlayers, StringProperties, NumericProperties, CountMultiple, IgnoreCountMultiple, AddMatchmakerPartySuccessDelegate, AddMatchmakerPartyErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnAddMatchmakerPartySuccess(FNakamaPartyMatchmakerTicket Ticket)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined matchmaker as party: %s"), *Ticket.Ticket);
}

void ASagiShiActor::OnAddMatchmakerPartyError(const FNakamaRtError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error matchmaking as party: %s"), *Error.Message);
}

Sending party data #

Sagi-shi players can send data to other members of their party to indicate they wish to start a vote.

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USTRUCT()
struct FVoteState
{
	GENERATED_BODY()

public:
	UPROPERTY()
	FString Username;

	UPROPERTY()
	FString Reason
};

// ...

#define OPCODE_CALL_VOTE 6

FVoteState VoteState;
VoteState.Username = TEXT("<Username>");
VoteState.Reason = TEXT("Emergency");

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(VoteState, Json);

RealtimeClient->SendPartyData(Party.Id, OPCODE_CALL_VOTE, Json);

Receiving party data #

Sagi-shi players can receive party data from other party members by subscribing to the party data event.

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FOnReceivedPartyData ReceivedPartyDataDelegate;
ReceivedPartyDataDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedPartyData);

RealtimeClient->PartyDataCallback = ReceivedPartyDataDelegate;
RealtimeClient->SetListenerPartyDataCallback();

/* Delegate handlers */

void ASagiShiActor::OnReceivedPartyData(const FNakamaPartyData& PartyData)
{
	switch (PartyData.OpCode)
	{
	case OPCODE_CALL_VOTE:
		FVoteState VoteState;
		FJsonObjectConverter::JsonObjectStringToUStruct(PartyData.Data, &VoteState);

		// Show a UI dialogue - "<username> has proposed to call a vote for <reason>. Do you agree? Yes/No"
		break;
	default:
		UE_LOG(LogTemp, Error, TEXT("Unsupported opcode"));
		break;
	}
}

Leaderboards #

Nakama Leaderboards introduce a competitive aspect to your game and increase player engagement and retention.

Sagi-shi has a leaderboard of weekly imposter wins, where player scores increase each time they win, and similarly a leaderboard for weekly crew member wins.

Sagi-shi leaderboard screen
Sagi-shi Leaderboard

Creating leaderboards #

Leaderboards have to be created on the server, see the leaderboard documentation for details on creating leaderboards.

Submitting scores #

When players submit scores, Nakama will increment the player’s existing score by the submitted score value.

Along with the score value, Nakama also has a subscore, which can be used for ordering when the scores are the same.

Sagi-shi players can submit scores to the leaderboard with contextual metadata, like the map the score was achieved on:

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USTRUCT()
struct FLeaderboardMetadata
{
	GENERATED_BODY()

public:
	UPROPERTY()
	FString Map;
};

int32 Score = 1;
int32 SubScore = 0;

FLeaderboardMetadata LeaderboardMetadata;
LeaderboardMetadata.Map = "space_station";

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(LeaderboardMetadata, Json);

FOnWriteLeaderboardRecord WriteLeaderboardRecordSuccessDelegate;
WriteLeaderboardRecordSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnWriteLeaderboardRecordSuccess);

FOnError WriteLeaderboardRecordErrorDelegate;
WriteLeaderboardRecordErrorDelegate.AddDynamic(this, &ASagiShiActor::OnWriteLeaderboardRecordError);

Client->WriteLeaderboardRecord(Session, TEXT("for_all"), Score, SubScore, Json, WriteLeaderboardRecordSuccessDelegate, WriteLeaderboardRecordErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnWriteLeaderboardRecordSuccess(const FNakamaLeaderboardRecord& Record)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully wrote leaderboard record"));
}

void ASagiShiActor::OnWriteLeaderboardRecordError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error writing leaderboard record: %s"), *Error.Message);
}

Listing the top records #

Sagi-shi players can list the top records of the leaderboard:

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int32 Limit = 20;
FString LeaderboardId = "weekly_imposter_wins";
TArray<FString> OwnerIds = {};
FString Cursor = TEXT("");

FOnListLeaderboardRecords ListLeaderboardRecordsSuccessDelegate;
ListLeaderboardRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsSuccess);

FOnError ListLeaderboardRecordsErrorDelegate;
ListLeaderboardRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsError);

Client->ListLeaderboardRecords(Session, LeaderboardId, OwnerIds, Limit, Cursor, ENakamaLeaderboardListBy::BY_SCORE, ListLeaderboardRecordsSuccessDelegate, ListLeaderboardRecordsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListLeaderboardRecordsSuccess(const FNakamaLeaderboardRecordList& RecordsList)
{
	for (int16 i = 0; i < RecordsList.Records.Num(); i++)
	{
		FNakamaLeaderboardRecord Record = RecordsList.Records[i];
		UE_LOG(LogTemp, Log, TEXT("%s: %d"), *Record.OwnerId, Record.Score);
	}
}

void ASagiShiActor::OnListLeaderboardRecordsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing leaderboard records: %s"), *Error.Message);
}

Listing records around the user

Nakama allows developers to list leaderboard records around a player.

Sagi-shi gives players a snapshot of how they are doing against players around them:

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int32 Limit = 20;
FString LeaderboardId = "weekly_imposter_wins";
FString Cursor = TEXT("");

FOnListLeaderboardRecords ListLeaderboardRecordsSuccessDelegate;
ListLeaderboardRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsSuccess);

FOnError ListLeaderboardRecordsErrorDelegate;
ListLeaderboardRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsError);

Client->ListLeaderboardRecordsAroundOwner(Session, LeaderboardId, Session->SessionData.UserId, Limit, ListLeaderboardRecordsSuccessDelegate, ListLeaderboardRecordsErrorDelegate);

Listing records for a list of users

Sagi-shi players can get their friends’ scores by supplying their user ids to the owner id parameter:

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void ASagiShiActor::OnGetFriendsSuccess(FNakamaFriendList Friends)
{
	TArray<FString> FriendIds;

	for (int16 i = 0; i < Friends.NakamaUsers.Num(); i++)
	{
		FriendIds.Add(Friends.NakamaUsers[i].NakamaUser.Id);
	}

	int32 Limit = 20;
	FString LeaderboardId = "weekly_imposter_wins";
	FString Cursor = TEXT("");

	FOnListLeaderboardRecords ListLeaderboardRecordsSuccessDelegate;
	ListLeaderboardRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsSuccess);

	FOnError ListLeaderboardRecordsErrorDelegate;
	ListLeaderboardRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsError);

	Client->ListLeaderboardRecords(Session, LeaderboardId, FriendIds, Limit, Cursor, ENakamaLeaderboardListBy::BY_SCORE, ListLeaderboardRecordsSuccessDelegate, ListLeaderboardRecordsErrorDelegate);
}

The same approach can be used to get group member’s scores by supplying their user ids to the owner id parameter:

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void ASagiShiActor::OnListGroupUsersSuccess(const FNakamaGroupUsersList& GroupUsers)
{
	TArray<FString> MemberIds;

	for (int16 i = 0; i < GroupUsers.GroupUsers.Num(); i++)
	{
		MemberIds.Add(GroupUsers.GroupUsers[i].User.Id);
	}

	int32 Limit = 20;
	FString LeaderboardId = "weekly_imposter_wins";
	FString Cursor = TEXT("");

	FOnListLeaderboardRecords ListLeaderboardRecordsSuccessDelegate;
	ListLeaderboardRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsSuccess);

	FOnError ListLeaderboardRecordsErrorDelegate;
	ListLeaderboardRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListLeaderboardRecordsError);

	Client->ListLeaderboardRecords(Session, LeaderboardId, MemberIds, Limit, Cursor, ENakamaLeaderboardListBy::BY_SCORE, ListLeaderboardRecordsSuccessDelegate, ListLeaderboardRecordsErrorDelegate);
}

Deleting records #

Sagi-shi players can delete their own leaderboard records:

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FOnDeletedLeaderboardRecord DeleteLeaderboardRecordSuccessDelegate;
DeleteLeaderboardRecordSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteLeaderboardRecordSuccess);

FOnError DeleteLeaderboardRecordErrorDelegate;
DeleteLeaderboardRecordErrorDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteLeaderboardRecordError);

Client->DeleteLeaderboardRecord(Session, TEXT("<LeaderboardId>"), DeleteLeaderboardRecordSuccessDelegate, DeleteLeaderboardRecordErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnDeleteLeaderboardRecordSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully deleted leaderboard record"));
}

void ASagiShiActor::OnDeleteLeaderboardRecordError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error deleting leaderboard record: %s"), *Error.Message);
}

Tournaments #

Nakama Tournaments are short lived competitions where players compete for a prize.

Sagi-shi players can view, filter and join running tournaments.

Sagi-shi tournaments screen
Sagi-shi Tournaments

Creating tournaments #

Tournaments have to be created on the server, see the tournament documentation for details on how to create a tournament.

Sagi-shi has a weekly tournament which challenges players to get the most correct imposter votes. At the end of the week the top players receive a prize of in-game currency.

Joining tournaments #

By default in Nakama players don’t have to join tournaments before they can submit a score, but Sagi-shi makes this mandatory:

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FOnJoinedTournament JoinTournamentSuccessDelegate;
JoinTournamentSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnJoinTournamentSuccess);

FOnError JoinTournamentErrorDelegate;
JoinTournamentErrorDelegate.AddDynamic(this, &ASagiShiActor::OnJoinTournamentError);

Client->JoinTournament(Session, TEXT("<TournamentId>"), JoinTournamentSuccessDelegate, JoinTournamentErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnJoinTournamentSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully joined tournament"));
}

void ASagiShiActor::OnJoinTournamentError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error joining tournament: %s"), *Error.Message);
}

Listing tournaments #

Sagi-shi players can list and filter tournaments with various criteria:

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int32 CategoryStart = 1;
int32 CategoryEnd = 2;
int32 StartTime = 0;
int32 EndTime = 0;
int32 Limit = 100;
FString Cursor = TEXT("");

FOnListTournaments ListTournamentsSuccessDelegate;
ListTournamentsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentsSuccess);

FOnError ListTournamentsErrorDelegate;
ListTournamentsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentsError);

Client->ListTournaments(Session, CategoryStart, CategoryEnd, StartTime, EndTime, Limit, Cursor, ListTournamentsSuccessDelegate, ListTournamentsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListTournamentsSuccess(const FNakamaTournamentList& Tournaments)
{
	for (int16 i = 0; i < Tournaments.Tournaments.Num(); i++)
	{
		FNakamaTournament Tournament = Tournaments.Tournaments[i];
		UE_LOG(LogTemp, Log, TEXT("%s: %s"), *Tournament.Id, *Tournament.Title);
	}
}

void ASagiShiActor::OnListTournamentsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing tournaments: %s"), *Error.Message);
}

For performance reasons categories are filtered using a range, not individual numbers. Structure your categories to take advantage of this (e.g. all PVE tournaments in the 1XX range, all PVP tournaments in the 2XX range, etc.).

Listing records #

Sagi-shi players can list tournament records:

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int32 Limit = 20;
FString TournamentId = TEXT("weekly_top_detectives");
FString Cursor = TEXT("");
TArray<FString> OwnerIds = {};

FOnListTournamentRecords ListTournamentRecordsSuccessDelegate;
ListTournamentRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentRecordsSuccess);

FOnError ListTournamentRecordsErrorDelegate;
ListTournamentRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentRecordsError);

Client->ListTournamentRecords(Session, TournamentId, Limit, Cursor, OwnerIds, ENakamaLeaderboardListBy::BY_SCORE, ListTournamentRecordsSuccessDelegate, ListTournamentRecordsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListTournamentRecordsSuccess(const FNakamaTournamentRecordList& RecordsList)
{
	for (int16 i = 0; i < RecordsList.Records.Num(); i++)
	{
		FNakamaLeaderboardRecord Record = RecordsList.Records[i];
		UE_LOG(LogTemp, Log, TEXT("%s: %d"), *Record.OwnerId, Record.Score);
	}
}

void ASagiShiActor::OnListTournamentRecordsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing tournament records: %s"), *Error.Message);
}

Listing records around a user

Similarly to leaderboards, Sagi-shi players can get other player scores around them:

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int32 Limit = 20;
FString TournamentId = TEXT("weekly_top_detectives");
FString Cursor = TEXT("");
TArray<FString> OwnerIds = {};

FOnListTournamentRecords ListTournamentRecordsSuccessDelegate;
ListTournamentRecordsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentRecordsSuccess);

FOnError ListTournamentRecordsErrorDelegate;
ListTournamentRecordsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListTournamentRecordsError);

Client->ListTournamentRecordsAroundOwner(Session, TournamentId, Session->SessionData.UserId, Limit, ListTournamentRecordsSuccessDelegate, ListTournamentRecordsErrorDelegate);

Submitting scores #

Sagi-shi players can submit scores, subscores and metadata to the tournament:

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int32 Score = 1;
int32 SubScore = 0;

FLeaderboardMetadata LeaderboardMetadata;
LeaderboardMetadata.Map = "space_station";

FString Json;
FJsonObjectConverter::UStructToJsonObjectString(LeaderboardMetadata, Json);

FOnWriteLeaderboardRecord WriteTournamentRecordSuccessDelegate;
WriteTournamentRecordSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnWriteTournamentRecordSuccess);

FOnError WriteTournamentRecordErrorDelegate;
WriteTournamentRecordErrorDelegate.AddDynamic(this, &ASagiShiActor::OnWriteTournamentRecordError);

Client->WriteTournamentRecord(Session, TEXT("weekly_top_detective"), Score, SubScore, Json, WriteTournamentRecordSuccessDelegate, WriteTournamentRecordErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnWriteTournamentRecordSuccess(const FNakamaLeaderboardRecord& Record)
{
	UE_LOG(LogTemp, Log, TEXT("Successfully wrote tournament record"));
}

void ASagiShiActor::OnWriteTournamentRecordError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error writing tournament record: %s"), *Error.Message);
}

Notifications #

Nakama Notifications can be used for the game server to broadcast real-time messages to players.

Notifications can be either persistent (remaining until a player has viewed it) or transient (received only if the player is currently online).

Sagi-shi uses Notifications to notify tournament winners about their winnings.

Sagi-shi notification screen
Sagi-shi notifications

Receiving notifications #

Notifications have to be sent from the server.

Nakama uses a code to differentiate notifications. Codes of 0 and below are system reserved for Nakama internals.

Sagi-shi players can subscribe to the notification received event. Sagi-shi uses a code of 100 for tournament winnings:

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FOnReceivedNotification NotificationReceivedDelegate;
NotificationReceivedDelegate.AddDynamic(this, &ASagiShiActor::OnReceivedNotification);

RealtimeClient->NotificationReceived = NotificationReceivedDelegate;
RealtimeClient->SetListenerNotificationsCallback();

/* Delegate handlers */

void ASagiShiActor::OnReceivedNotification(const FNakamaNotificationList& NotificationList)
{
	const int32 RewardCode = 100;

	for (int16 i = 0; i < NotificationList.Notifications.Num(); i++)
	{
		FNakamaNotification Notification = NotificationList.Notifications[i];
		switch (Notification.Code)
		{
		case RewardCode:
			UE_LOG(LogTemp, Log, TEXT("Congratulations, you won the tournament!\n%s"), *Notification.Subject, *Notification.Content);
			break;
		default:
			UE_LOG(LogTemp, Log, TEXT("Other notification: %s\n%s"), *Notification.Subject, *Notification.Content);
			break;
		}
	}
}

Listing notifications #

Sagi-shi players can list the notifications they received while offline:

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int32 Limit = 100;
FString Cursor = TEXT("");

FOnListNotifications ListNotificationsSuccessDelegate;
ListNotificationsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnListNotificationsSuccess);

FOnError ListNotificationsErrorDelegate;
ListNotificationsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnListNotificationsError);

Client->ListNotifications(Session, Limit, Cursor, ListNotificationsSuccessDelegate, ListNotificationsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnListNotificationsSuccess(FNakamaNotificationList NotificationList)
{
	for (int16 i = 0; i < NotificationList.Notifications.Num(); i++)
	{
		FNakamaNotification Notification = NotificationList.Notifications[i];
		UE_LOG(LogTemp, Log, TEXT("Notification: %s\n%s"), *Notification.Subject, *Notification.Content);
	}
}

void ASagiShiActor::OnListNotificationsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error listing notifications: %s"), *Error.Message);
}

Pagination and cacheable cursors

Like other listing methods, notification results can be paginated using a cursor or cacheable cursor from the result.

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FString CacheableCursor = NotificationList.CacheableCursor;

The next time the player logs in the cacheable cursor can be used to list unread notifications.

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Client->ListNotifications(Session, Limit, CacheableCursor, ListNotificationsSuccessDelegate, ListNotificationsErrorDelegate);

Deleting notifications #

Sagi-shi players can delete notifications once they’ve read them:

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TArray<FString> NotificationIds;

FOnDeleteNotifications DeleteNotificationsSuccessDelegate;
DeleteNotificationsSuccessDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteNotificationsSuccess);

FOnError DeleteNotificationsErrorDelegate;
DeleteNotificationsErrorDelegate.AddDynamic(this, &ASagiShiActor::OnDeleteNotificationsError);

Client->DeleteNotifications(Session, NotificationIds, DeleteNotificationsSuccessDelegate, DeleteNotificationsErrorDelegate);

/* Delegate handlers */

void ASagiShiActor::OnDeleteNotificationsSuccess()
{
	UE_LOG(LogTemp, Log, TEXT("Successfully deleted notifications"));
}

void ASagiShiActor::OnDeleteNotificationsError(const FNakamaError& Error)
{
	UE_LOG(LogTemp, Error, TEXT("Error deleting notifications: %s"), *Error.Message);
}