Nakama Defold Client Guide #

This client library guide will show you how to use the core Nakama features in Defold 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

Prerequisites #

Before proceeding ensure that you have:

Add the client to your project #

Add the URL of a client release .zip as a library dependency to game.project. The client will now show up as a nakama folder in your project.

Add Defold plugins #

Defold projects additionally require the following modules:

Asynchronous programming #

Many of the Nakama APIs are asynchronous and non-blocking and can be used in the Defold SDK through callback functions or Nakama sync functions.

Sagi-shi can call Nakama functions with or without a callback function:

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-- blocking
local nakama.get_account(client)

-- non-blocking
nakama.get_account(client, function(account)
  print(account.user.id)
end)

The Nakama client provides a convenience function for creating and starting a coroutine to run multiple requests synchronously:

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-- non-blocking coroutine
nakama.sync(function()
  -- blocks in the coroutine
  local client = nakama.create_client(config)
  -- blocks in the coroutine
  local nakama.get_account(client)
end)

Handling errors #

Network programming requires additional safeguarding against connection and payload issues.

The server and the client can generate logs which are helpful for debugging.

To enable verbose logging from the client:

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log = require "nakama.util.log"
-- enable trace logging in nakama client
log.print()

For production use

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log.silent() -- disable trace logging in nakama client

API calls in Sagi-shi return a result, which could contain an error property you can test for to gracefully handle errors:

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local result = nakama.get_account(client)

if result.error then
    print(result.message)
    return
end

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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local defold = require "nakama.engine.defold"

local config = {
  host = 127.0.0.1,
  port = 7350,
  use_ssl = false,
  username = "defaultkey",
  engine = defold
}

local client = nakama.create_client(config)

Nakama Socket #

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

Use the client and create a socket:

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local socket = nakama.create_socket(client)

nakama.sync(function()
    -- connect
    local ok, err = nakama.socket_connect(socket)

    if ok then
      -- do socket stuff
    end

    if err then
      print(err.message)
    end
end)

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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local nakama_session = require "nakama.session"

function authenticate_with_device()
  nakama.sync(function()
    local vars = nil
    local create = true
    local result = nakama.authenticate_device(client, defold.uuid(), vars, create, "mycustomusername")

    if not result.token then
      print("Unable to login")
      return
    end

    -- store the token to use when communicating with the server
    nakama.set_bearer_token(client, result.token)

    -- store the toke on disk

    local session = nakama_session.create(token)
    print(session.user_id)
  end)
end

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.

Install the official Facebook SDK for Defold (external) to use Nakama Facebook Authentication.
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local nakama_session = require "nakama.session"

function authenticate_with_facebook()
  -- Facebook permissions
  local permissions = { "public_profile" }

  -- you don't need a publishing audience with read permissions
  local audience = facebook.AUDIENCE_NONE

  facebook.login_with_permissions(permissions, audience, function(self, data)
    local vars = nil
    local create = true
    local result = nakama.authenticate_facebook(client, facebook.access_token(), vars, create, "mycustomusername")

    if not result.token then
      print("Unable to login")
      return
    end

    -- store the token to use when communicating with the server
    nakama.set_bearer_token(client, result.token)

    -- store the token on disk

    local session = nakama_session.create(token)
    print(session.user_id)
  end)
end

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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function link_device_authentication()
  local result = nakama.link_device(client, defold.uuid())

  if result.error
    print(result.error)
    return
  end
end

Linking Facebook authentication

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function link_facebook_authentication()
  -- Facebook permissions
  local permissions = { "public_profile" }

  -- you don't need a publishing audience with read permissions
  local audience = facebook.AUDIENCE_NONE

  facebook.login_with_permissions(permissions, audience, function(self, data)
    local result = nakama.link_facebook(client, facebook.access_token())

    if result.error
      print(result.error)
      return
    end
  end)
end

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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local vars = {
  device_os = SystemInfo.operatingSystem,
  devic_model = SystemInfo.deviceModel,
  game_version = Application.version,
  inviter_user_id = "<SomeUserId>"
}

local result = nakama.authenticate_device(client, defold.uuid(), vars)

To access session variables on the Client use the vars property on the Session object:

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local device_os = session.vars.device_os

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.

Sagi-shi stores the auth token on disk:

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sys.save(session.token, "token_path")

Restore a session without having to re-authenticate:

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local nakama_session = require "nakama.session"

local token = sys.load("token_path")
local session = nakama_session.create(token)

if nakama_session.expired(session) then
  print("Session has expired, re-authenticate.")
else
  nakama.set_bearer_token(client, session.token)
end

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

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local time_one_day = 60 * 60 * 24

-- check whether a session has expired or is close to expiry.
if nakama_session.expired(session) or os.difftime(session.expires, os.time()) < time_one_day then
  local result = nakama.session_refresh(client, session.token, vars)

  -- authenticate
  if result.error then
    local result = nakama.authenticate_device(client, defold.uuid(), true)
  end
end

Ending sessions #

Logout and end the current session:

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local result = nakama.session_logout(client, session.refresh_token, session.token)

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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local result = nakama.get_account(client)

if result.error then
    print(result.message)
    return
end

local user = result.user
local username = user.username
local avatar_url = user.avatar_url
local user_id = user.id

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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local newUsername = "NotTheImp0ster"
local display_name = "Innocent Dave"
local avatar_url = "https://example.com/imposter.png"
local lang_tag = "en"
local location = "Edinburgh"
local timezone = "BST"

local result = nakama.update_account(client, avatar_url, display_name, lang_tag, location, timezone, newUsername)

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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local ids = { "userid1", "userid2" }
local usernames = { "username1", "username2" }
local facebook_ids = { "facebookid1" }

local result = nakama.get_users(client, ids, usernames, facebook_ids)

if result.error then
  print(result.message)
  return
end

local users = result.users

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 #

Read the user account and their metadata will already by decoded in a table:

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local result = nakama.get_account(client)

local title = result.user.metadata.title
local hat = result.user.metadata.hat
local skin = result.user.metadata.skin

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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local account = nakama.get_account(client)
local wallet = json.decode(account.wallet)
print("Wallet:")
for currency, amount in pairs(wallet) do
	print(currency .. ": " .. amount)
end

Updating wallets #

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

Validating in-app purchases #

Sagi-shi players can purchase the virtual in-game currency through in-app purchases that are authorized and validated to be legitimate on the server.

See the In-app Purchase Validation documentation for examples.

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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local user_id = user.id

local objects = {
  {
    collection = "Unlocks",
    key = "Hats",
    userId = user_id
  }
}
local result = nakama.read_storage_objects(client, objects)

if result.error then
  print(result.message)
  return
end

for _,object in ipairs(result.objects) do
  pprint(object)
end
To read other players’ public storage object, use their user id instead. Players can only read storage objects they own or that are public (Read permission 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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local objects = {
  {
    collection = "Favorites",
    key = "Hats",
    value = json.encode({ "cowboy", "alien" }),
    permissionRead = 1,
    permissionWrite = 1,
    version = ""
  }
}
local result = nakama.write_storage_objects(client, objects)

if result.error then
    print(result.message)
    return
end

for _,ack in ipairs(result.acks) do
  pprint(ack)
end

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 (storage_object)
local objects = {
  {
    collection = storage_object.collection,
    key = storage_object.key,
    value = json.encode({ "cowboy", "alien" }),
    permissionRead = 0,
    permissionWrite = 1,
    version = storage_object.version
  }
}

local result = nakama.write_storage_objects(client, objects)

if result.error then
  print(result.message)
  return
end

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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local user_id = user.id
local limit = 3

local result = nakama.list_storage_objects(client, "Unlocks", user_id, limit)

if result.error then
  print(result.message)
  return
end

local titles = nil
local hats = nil
local skins = nil

for k, object in pairs(result.objects)
  if object.key == "Titles" then
    local titles = object
  else if object.key == "Hats" then
    local hats = object
  else if object.key == "Skins" then
    local skins = object
  end
end

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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local next_result = nakama.list_storage_objects(client, "Unlocks", user_id, limit, result.cursor)

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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local payload = {
	item = "cowboy"
}
nakama.rpc_func(client, "EquipHat", json.encode(payload), nil, function(result)
	pprint(result)
end)

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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local ids = { "<SomeUserId>", "<AnotherUserId>" }
local usernames = { "AlwaysTheImposter21", "SneakyBoi" }

local result = nakama.add_friends(client, ids, usernames)

if result.error then
  print(result.message)
  return
end

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

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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local limit = 20 -- Limit is capped at 1000
local frienship_state = 0
local cursor = nil

local result = nakama.list_friends(client, limit, frienship_state, cursor)

if result.error then
  print(result.message)
  return
end

for _,friend in ipairs(result.friends) do
  pprint(friend)
end

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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local limit = 1000
local frienship_state = 2
local cursor = nil

local list_friends_result = nakama.list_friends(client, limit, frienship_state, cursor)

if list_friends_result.error then
  print(list_friends_result.message)
  return
end

local ids = {}

for _, friend in ipairs(list_friends_result.friends) do
  -- Collect all ids
  table.insert(ids, friend.id)
end

-- Accept all friends requests at once
local add_friends_result = nakama.add_friends(client, ids)

Deleting friends #

Sagi-shi players can decline friend requests and remove friends by their username or user id:

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local ids = { "<SomeUserId>", "<AnotherUserId>" }
local usernames = { "<SomeUsername>", "<AnotherUsername>" }

local result = nakama.delete_friends(client, ids, usernames)

if result.error then
  print(result.message)
  return
end

Blocking users #

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

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local ids = { "<SomeUserId>", "<AnotherUserId>" }
local usernames = { "<SomeUsername>", "<AnotherUsername>" }

local result = nakama.block_friends(client, ids, usernames)

if result.error then
  print(result.message)
  return
end

Blocked users can listed just like listing friends but using the corresponding friendship state (3).

Status & Presence #

Nakama Status & Presence is has 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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socket.on_statuspresence(function(message)
  local pressences = message.on_status_presence

  if pressence then
    -- todo: check if online
    for _, presence in ipairs(presences)
      pprint(presence.username .. " is online with status: '" .. presence.status .. "'")
    end
  end
end)

local user_ids = { "<SomeUserId>", "<AnotherUserId>" }
local result = socket.status_follow(user_ids)

if result.error then
  print(result.error.message)
  return
end

-- todo: check if list of presences received and print

Unfollow users #

Sagi-shi players can unfollow others:

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local user_ids = { "<SomeUserId>", "<AnotherUserId>" }
local result = socket.status_unfollow(user_ids)

Updating player status #

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

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local result = socket.status_update("Viewing the Main Menu")

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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local avatar_url = "https://example.com/imposter.png"
local description = "A group for people who love playing the imposter."
local lang_tag = "en"
local max_count = 100
local name = "Imposters R Us"
local open = true -- public group

local result = nakama.create_group(client, avatar_url, description, lang_tag, max_count, name, open)

if result.error then
  print(result.message)
  return
end

pprint(result.name)

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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local avatar_url = "https://example.com/imposter.png"
local description = "A group for people who love playing the imposter."
local group_id = "<GroupId>"
local lang_tag = "en"
local name = "Imposters R Us"
local open = false -- private group

local result = nakama.update_group(client, group_id, avatar_url, description, group_id, lang_tag, name, open)

if result.error then
  print(result.message)
  return
end

pprint(result.open)

Update group size #

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

See the updating group size 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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local name = "imposter%"
local limit = 20
cursor = nil

local result = nakama.list_groups(client, name, cursor, limit)

if result.error then
  print(result.message)
  return
end

for _, group in ipairs(result.groups) do
  pprint(group.name .. " " .. tostring(group.open))
end

-- Get the next page of results.
local next_result = nakama.list_groups(client, name, result.cursor, limit)

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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local result = nakama.delete_group(client, "<GroupId>")

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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local payload = {
	GroupId = "<GroupId>",
	Interests = { "Deception", "Sabotage", "Cute Furry Bunnies" },
	ActiveTimes = { "9am-2pm Weekdays", "9am-10pm Weekends" },
	Languages = { "English", "German" }
}

nakama.rpc_func(client, "UpdateGroupMetadata", json.encode(payload), nil, function()
	print("Successfully updated group metadata")
end)

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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local result = nakama.join_group(client, "<GroupId>")

Listing the user’s groups #

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

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local user_id = account.user.id
local limit = 20
local membership_state = nil -- All membership states
local cursor = nil

local result = list_user_groups(client, user_id, limit, membership_state, cursor)

if result.error then
  print(result.message)
  return
end

for _, group in ipairs(result.groups) do
  pprint(group.name .. " " .. tostring(group.state))
end

Listing members #

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

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local limit = 20
local membership_state = nil -- All membership states
local cursor = nil

local result = nakama.list_group_users(client, "<GroupId>", limit, membership_state, cursor);

if result.error then
  print(result.message)
  return
end

for _, group in ipairs(result.groups) do
  pprint(group.name .. " " .. tostring(group.state))
end

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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local limit = 20
local membership_state = 3 -- Join request
local cursor = nil

local list_group_result = nakama.list_group_users(client, "<GroupId>", limit, membership_state, cursor);

if list_group_result.error then
  print(list_group_result.message)
  return
end

local ids = {}

for _, user in ipairs(list_group_result.users) do
  -- Collect all ids
  table.insert(ids, user.id)
end

-- Accept all join requests at once
local add_friends_result = nakama.add_group_users(client, "<GroupId>", ids)

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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local result = nakama.promote_group_users(client, "<GroupId>", { "<SomeUserId>", "<AnotherUserId>" })

Demoting members #

Sagi-shi group admins and superadmins can demote members:

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local result = nakama.demote_group_users(client, "<GroupId>", { "<SomeUserId>", "<AnotherUserId>" })

Kicking members #

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

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local result = nakama.kick_group_users(client, "<GroupId>", { "<SomeUserId>", "<AnotherUserId>" })

Banning members #

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

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local result = nakama.ban_group_users(client, "<GroupId>", { "<SomeUserId>", "<AnotherUserId>" })

Leaving groups #

Sagi-shi players can leave a group:

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local result = nakama.leave_group(client, "<GroupId>")

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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local room_name = "<MatchId>"
local persistence = false
local hidden = false
local result = socket.channel_join(room_name, socket.CHANNELTYPE_ROOM, persistence, hidden)

print("Connected to dynamic room channel: " .. result.channel.id)

Joining group chat #

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

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local group_id = "<GroupId>"
local persistence = true
local hidden = false
local result = socket.channel_join(group_id, socket.CHANNELTYPE_GROUP, persistence, hidden)

print("Connected to group channel: " .. result.channel.id)

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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local user_id = "<UserId>"
local persistence = true
local hidden = false
local result = socket.channel_join(user_id, socket.CHANNELTYPE_DIRECT_MESSAGE, persistence, hidden)

print("Connected to direct message channel: " .. result.channel.id);

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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local channel_id = "<ChannelId>"

local content = {
  message = "I think Red is the imposter!"
}

local message_send_ack = socket.channel_message_send(channel_id, json.encode(content))

local emote_content = {
    emote = "point" ,
    emoteTarget = "<RedPlayerUserId>"
};

local emote_send_ack = socket.channel_message_send(channelId, json.encode(emote_content));

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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local limit = 100
local forward = true
local group_id = "<GroupId>"
local result = nakama.list_channel_messages(client, group_id, limit, forward)

for i,message in ipairs(result.messages) do
  print(("%s:%s"):format(message.username, message.content))
end

Chat also has cacheable cursors to fetch the most recent messages. Store the cursor in a persistent Lua table using sys.save()

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-- cache cursor in file 'my_settings'
local settings = sys.load("my_settings")
settings["nakama_message_cursor_" .. group_id] = result.cacheableCursor
sys.save("my_settings", settings)

-- get cached cursor
local settings = sys.load("my_settings")
local cursor = settings["nakama_message_cursor_" .. group_id]

-- use cursor to get new message
local next_result = nakama.list_channel_messages(client, group_id, limit, forward, cursor)

-- update cached cursor
settings["nakama_message_cursor_" .. group_id] = next_result.cacheableCursor
sys.save("my_settings", settings)

Updating messages #

Nakama also supports updating messages. It is up to you whether you want to use this feature, but in a game of deception like Sagi-shi it can add an extra element of deception.

For example a player sends the following message:

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local channelId = "<ChannelId>"
local message_content = {
    message = "I think Red is the imposter!"
};

local message_send_ack = socket.channel_message_send(channel_id, json.encode(message_content))

They then quickly edit their message to confuse others:

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local new_message_content =  {
    message = "I think BLUE is the imposter!"
}
local message_update_ack = socket.channel_message_update(channel_id, message_send_ack.message_id, json.encode(new_message_content))

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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local result = socket.match_create()

if result.error then
  print(result.error.message)
  return
end

local match_id = result.match_create.match_id

local limit = 20
local frienship_state = 0

local result = nakama.list_friends(client, limit, frienship_state)
-- todo: get online friends

if result.error then
  print(result.error.message)
  return
end

for _,friend in ipairs(result.friends) do
  pprint(friend)
  -- todo: send match_id to online friends
end

Joining matches #

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

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local match_id = "<MatchId>"
local result = socket.match_join(match_id)

if result.error then
  print(result.error.message)
  return
end

if result.match then
  print("Match joined!")
end

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

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local min_players = 2
local max_players = 10
local query = "*"

local result = socket.matchmaker_add(min_players, max_players, query)

if result.error then
  print(result.error.message)
  return
end

socket.on_matchmakermatched(function(message)
  local matched = message.matchmaker_matched

  if matched then
    print(matched.match_id)
    print(matched.token)
  end
end)

Joining matches from player status

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

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local status = {
  status = "Playing a match",
  match_id = "<MatchId>"
}

local result = socket.status_update(status)

if result.error then
  print(result.error.message)
  return
end

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

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socket.on_statuspresence(function(message)
  local pressence = message.on_status_presence

  if pressence then
    if presence.status.match_id then
      local match_id = presence.status.match_id

      local result = socket.match_join(match_id)
    end
  end
end)

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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local limit = 10
local authoritative = true
local label = ""
local min_size = 2
local max_size = 10
local query = ""

local result = nakama.list_matches(client, limit, authoritative, label, min_size, max_size, query)

if result.error then
  print(result.message)
  return
end

for _, match in ipairs(result.matches) do
  pprint(group.match_id .. ": " .. tostring(match.size) .. "/10 players")
end

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

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local label = "AnExactMatchLabel"

Advanced:

In order to use a more complex structured query, the match label must be in JSON format.

To find a match where it expects player skill level to be >100 and optionally has a game mode of "sabotage":

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local query = "+label.skill:>100 label.mode:sabotage"

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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local result = socket.match_join("<match_id>", account.token)

local players = {}

for _, presence in ipairs(result.match_join.presences)
  local player = add_player()
  players[presence.session_id] = player
end

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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socket.on_matchpresence(function(message)
  -- todo: check if it's joins
  for _, presence in ipairs(message.match_presence_event.joins)
    local player = add_player()
    players[presence.session_id] = player
  end

  -- todo: check if it's leaves
  for _, presence in ipairs(message.match_presence_event.leaves)
    players[presence.session_id] = nil
  end
end)

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

Grab the player’s position, set the op code and send the JSON encoded state:

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local data = json.encode({
  x = player.x,
  y = player.y,
})

local op_code = 1

local result = socket.match_data_send("<match_id>", op_code, data)

if result.error then
  print(result.error.message)
  pprint(result)
end

Op Codes as a table

Sagi-shi has many networked game actions. Using a static class of constants for op codes will keep your code easier to follow and maintain:

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local op_codes = {
  position = 1
  vote = 2
}

local result = socket.match_data_send("<match_id>", op_code.position, data)

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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socket.on_matchdata(function(message)
  local match_data = message.match_data
  local op_code = tonumber(match_data.op_code)
  local data = json.decode(match_data.data)

  if op_code == op_codes.positoon then
    -- todo: check what presence comes in
    local session_id = match_data.presence.session_id

    if players[session_id] then
      local player = players[session_id]

      player.x = data.x
      player.ya = data.y
    end
  else if op_code == op_codes.vote then
    -- vote logic
  end
end)

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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local query = "+skill:>100 mode:sabotage"
local min_count = 2
local max_count = 10
local string_properties = json.encode({ mode = "sabotage" })
local numeric_properties = json.encode({ skill = 125 })

local result = socket.matchmaker_add(min_count, max_count, query, string_properties, numeric_properties)

if result.error then
  print(result.error.message)
end

After being successfully matched according to the provided criteria, players can join the match:

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socket.on_matchmaker_matched(function(matched)
  pprint("Received:", matched);
  socket.match_join(matched.token)
end)

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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local open = false
local max_players = 4
local party = socket.party_create(open, max_players)

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

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local result = nakama.list_friends(client, 100, 0)

for i,friend in ipairs(result.friends) do
  if friend.user.online then
    local content = {
      message = message = ("Hey %s, wanna join the party?!"):format(friend.user.username),
      partyId = party.party_id
    }

    local result = socket.channel_join(friend.user.id, 0)
    socket.channel_message_send(result.channel.id, json.encode(content))
  end
end

Joining parties #

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

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socket.on_channel_message(function(message)
  if message.party_id then
    socket.party_join(message.party_id)
  end
end)

Promoting a member #

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

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var newLeader = party.Presences.Where(p => p.SessionId != party.Leader.SessionId).First();
await socket.PromotePartyMemberAsync(party.Id, newLeader);

Leaving parties #

Sagi-shi players can leave parties:

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socket.party_leave(party.party_id)

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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socket.on_matchmaker_matched(function(message)
  socket.match_join(message.match_id)
end)

The party leader will start the matchmaking for their party:

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local min_players = 2
local max_players = 10
local query = ""
local ticket = socket.party_matchmaker_add("<PartyId>", min_players, max_players, query)

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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local data = json.encode({
  username = "<Username>",
  reason = "Emergency"
})

local vote_op_code = 6

local result = socket.party_data_send("<party_id>", vote_op_code, data)

if result.error then
  print(reuslt.error.message)
  pprint(result)
end

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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socket.on_party_data(function(message)
  local party_data = message.party_data
  local op_code = tonumber(party_data.op_code)
  local data = json.decode(party_data.data)

  if op_code == vote_op_code then
    -- Show a UI dialogue - "<username> has proposed to call a vote for <reason>. Do you agree? Yes/No"
  end
end)

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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local metadata = json.encode({ map = "space_station" })

-- need to be strings
local score = "1"
local subscore = "0"

nakama.write_leaderboard_record(client, "<leaderboard_id>", metadata, nil, score, subscore)

Listing the top records #

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

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local owner_ids = nil
local limit = 20
local cursor = nil
local expiry = nil

local result = nakama.list_leaderboard_records(client, "<leaderboard_id>", owner_ids, limit, cursor, expiry)

if result.error then
  print(result.error.message)
  return
end

for _, record in ipairs(result.leaderboard_records)
  print(record.owner_id .. ":" .. record.score)
end

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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local owner_ids = { "<SomeUserId>", "<AnotherUserId>" }
local limit = 5
local cursor = nil
local expiry = nil

local result = nakama.list_leaderboard_records_around_owner(client, "<leaderboard_id>", owner_ids, limit, cursor, expiry)

if result.error then
  print(result.error.message)
  return
end

for _, record in ipairs(result.leaderboard_records_around_owner)
  print(record.owner_id .. ":" .. record.score)
end

For example, if the leaderboard contains 100 records and the ownerId = “player123” with limit = 5, the result will include the specified user along with nearby records:

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{
  "records": [
    { "ownerId": "player120", "rank": 48, "score": 1500 },
    { "ownerId": "player121", "rank": 49, "score": 1480 },
    { "ownerId": "player123", "rank": 50, "score": 1450 },  // Your ownerId
    { "ownerId": "player125", "rank": 51, "score": 1430 },
    { "ownerId": "player127", "rank": 52, "score": 1400 }
  ]
}

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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nakama.list_leaderboard_records(client, "<leaderboard_id>", owner_ids)

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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local result = nakama.list_group_users(client, "<GroupId>", 100)
local user_ids = {}
for i,group_user in ipairs(result.groupUsers) do
  if group_user.state < 3 then
    table.insert(user_ids, group_user.user.id)
  end
end

local result = nakama.list_leaderboard_records(client, "weekly_imposter_wins", user_ids, 100)
for i,record in ipairs(result.records) do
  print(record.username, record.score)
end

Deleting records #

Sagi-shi players can delete their own leaderboard records:

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local result = nakama.delete_leaderboard_record(client, "<leaderboard_id>")

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]../../concepts/tournaments/#create-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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local result = nakama.join_tournament(client, "<tournament_id>")

Listing tournaments #

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

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local category_start = 1
local category_end = 2
local start_time = nil
local end_time = nil
local limit = 100
local cursor = nil

local result = nakama.list_tournaments(client, category_start, category_end, start_time, end_time, limit, cursor)

if result.error then
  print(result.error.message)
  return
end

for _, tournament in ipairs(result.tournaments)
  print(tournament.id .. ":" .. tournament.title)
end
Categories are filtered using a range, not individual numbers, for performance reasons. 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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local owner_ids = nil
local limit = 20
local cursor = nil
loca expiry = nil

local result = list_tournament_records(client, "<tournament_id>", owner_ids, limit, cursor, expiry)

if result.error then
  print(result.error.message)
  return
end

for _, record in ipairs(result.tournament_record)
  print(record.owner_id .. ":" .. record.score)
end

Listing records around a user

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

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local owner_ids = { "<SomeUserId>", "<AnotherUserId>" }
local limit = 20
local cursor = nil
loca expiry = nil

local result = nakama.list_tournament_records(client, "<tournament_id>", owner_ids, limit, cursor, expiry)

if result.error then
  print(result.error.message)
  return
end

for _, record in ipairs(result.tournament_record)
  print(record.owner_id .. ":" .. record.score)
end

Submitting scores #

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

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local metadata = json.encode({ map = "space_station" })
local score = 1
local subscore = 0

local result = nakama.write_tournament_record(client, "<tournament_id>", metadata, nil, score, subscore)

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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socket.on_notification(function(message)
  local reward_code = 100
  local notification = message.notification

  if notification.code == reward_code then
    print("Congratulations, you won the tournament!\n" .. notification.subject .. "\n" .. notification.content)
  else
    print(notification.code .. "\n" .. notification.subject .. "\n" .. notification.content)
  end
end)

Listing notifications #

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

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local limit = 100
local cacheable_cursor = nil

local result = nakama.list_notifications(client, limit, cacheable_cursor)

if result.error then
  print(result.error.message)
  return
end

for _, notification in ipairs(result.notifications)
  print(notification.code .. "\n" .. notification.subject .. "\n" .. notification.content)
end

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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_G.notifications = {
  cacheable_cursor = result.cacheable_cursor
}

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

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local cacheable_cursor = _G.notifications.cacheable_cursor
local next_results = list_notifications(client, limit, cacheable_cursor)

Deleting notifications #

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

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local result = nakama.delete_notifications(client, { "<notification_id_1>", "<notification_id_2>" })