Platform Sample Game Server (C#)

REST backend for the Enjin Farmer Unity sample (platform-sample-game-client-unity), demonstrating how to integrate NFTs into a game using the Enjin Platform C# SDK.

This is a rewrite of the previous Node.js server in .NET 9, preserving the route paths and JWT handling. One deliberate wire change came with SDK v3: token amount fields on the mint / melt / transfer endpoints are sent as decimal strings (the SDK uses BigInteger for token amounts), so the matching Unity client sends them as strings too.

What this server does

• Holds the Enjin Platform API key. The Unity client never sees it.
• Bootstraps an on-chain collection and a fixed set of resource tokens the game uses (Gold Coin, Gold Coin Blue, Green Gem) on first run.
• Issues players a JWT after /api/auth/register so subsequent calls can identify them.
• Creates a managed wallet per player (one managed wallet per externalId, where externalId == email) and drips a small amount of ENJ to it so it can pay transaction fees.
• Brokers mint / melt / transfer mutations to the platform and waits for on-chain finalization before responding to the client.

Prerequisites

• .NET 9 SDK.
• The Enjin Platform C# SDK v3.0.0 or later, pulled from NuGet automatically on dotnet restore. (For local development against an unreleased SDK, swap the PackageReference in PlatformSampleGameServer.csproj for the commented-out ProjectReference and check the SDK out as a sibling directory.)
• An Enjin Platform account and a generated API token.
• A running Wallet Daemon configured with the same API token; its SS58 address is what you'll set as DaemonWalletAddress below.
• cENJ in the daemon's wallet (use the Canary Faucet) to pay for collection creation, mints, and drips to new players.

Setup

1. Clone the repo:

   git clone https://github.com/enjin/platform-sample-game-server.git
   cd platform-sample-game-server

2. Create a local config:

   Copy appsettings.Sample.json to appsettings.Local.json (gitignored) and fill in:

   • Jwt.Secret — any long random string (32+ chars).
   • Enjin.ApiToken — your platform API token.
   • Enjin.DaemonWalletAddress — the SS58 address of your running wallet daemon, on the same network/chain (default Canary Matrix; uses SS58 prefix 9030).

   You can leave the rest of appsettings.json alone. Notable defaults:

   Setting	Default	Meaning
   Server.Port	3000	HTTP listen port. The Unity client expects 3000 by default.
   Enjin.Network / Enjin.Chain	Canary / Matrix
   Enjin.ResourceTokens	three entries	The Unity client has matching EnjinItem assets for Id 1, 2, 3.
   Enjin.CollectionName	Enjin Sample Game	Used to find or reuse an existing collection so you don't create a new one every run.
   Enjin.Ss58Prefix	9030	Matrix prefix; change if you target a different chain.
   Enjin.DripEnjEnabled / Enjin.DripEnjAmount	true / "1"	Each new managed wallet gets 1 ENJ from the daemon so it can pay fees.

3. Run the server:

   dotnet run

   On first launch the server:

   1. Looks for an existing collection owned by the daemon and named Enjin.CollectionName. If absent, creates one and waits for the CreateCollection transaction to finalize (~10–20s).
   2. Creates each entry in Enjin.ResourceTokens as a token in that collection. (Skipped on subsequent runs.)
   3. Persists the resulting collectionId to state.json so subsequent runs reuse it.

   When you see Server listening on http://0.0.0.0:3000 it's ready.

4. Stamp the collection ID into the Unity client.

   In the Unity Editor, run:

   Enjin → Stamp Collection ID onto EnjinItem Assets

   The Editor calls GET /api/setup/collection-id, then writes the value onto every EnjinItem ScriptableObject (Gold Coin, Gold Coin Blue, Green Gem). Commit those .asset files. Do this once after first server bootstrap, and again if the canary state ever resets and forces a new collection.

   If you skip this step, the Unity backpack UI will show no tokens because it filters by (collectionId, tokenId) against your wallet's holdings.

Optional flags

• dotnet run -- --skip-bootstrap — start the HTTP server without trying to allocate a collection. Useful when canary is misbehaving and you just want to inspect requests.

API endpoints

Method	Path	Auth	Purpose
GET	/api/auth/health-check	none	Liveness probe.
POST	/api/auth/register	none	Register or log in (same call). Returns a JWT.
GET	/api/wallet/get-tokens	JWT	Player's managed wallet + the resource-token balances they hold.
POST	/api/token/mint	JWT	Daemon-signed mint of tokenId into the caller's managed wallet.
POST	/api/token/melt	JWT	Player-signed burn of tokenId from the caller's managed wallet.
POST	/api/token/transfer	JWT	Player-signed transfer of tokenId to an SS58 address.
GET	/api/setup/collection-id	none	One-shot read used by the Unity Editor setup menu. Returns {"collectionId":"..."}.

Every JWT-protected route reads the email claim (the player identifier) and uses it as the externalId when talking to the Enjin Platform's managed-wallet APIs.

Source map

Path	Purpose
Program.cs	Host setup, DI registration, JWT configuration, bootstrap orchestration, port binding.
Services/EnjinService.cs	Every SDK call: collection bootstrap, managed wallet resolution, mint/melt/transfer, transaction polling, ENJ drip. Also defines ServerState, the persisted state (state.json) holding the collection id and the set of externalIds already dripped.
Services/AuthService.cs	Bcrypt password hashing, JWT issuance (sub + email claims).
Services/SubstrateAddress.cs	SS58 encoder (Blake2b + base58check) used to convert managed-wallet public keys returned by the platform into SS58 addresses.
Services/Options.cs	Strongly-typed config classes bound from appsettings*.json.
Endpoints/AuthEndpoints.cs	/api/auth/* minimal-API routes.
Endpoints/WalletEndpoints.cs	/api/wallet/* routes.
Endpoints/TokenEndpoints.cs	/api/token/* routes.
Endpoints/SetupEndpoints.cs	/api/setup/* routes (called by Unity Editor tooling).
Models/Dtos.cs	Request/response records (*Dto, *Request, *Response).
tools/Ss58SelfTest/	Tiny console app that verifies the SS58 encoder against published Polkadot/Substrate test vectors. Run with dotnet run --project tools/Ss58SelfTest.

appsettings.Local.json, state.json, and bin/ obj/ are gitignored.

Further reading

• Enjin Platform C# SDK
• Enjin Farmer setup guide
• Implementation breakdown