# Node Extensions

Extensions are optional modules a node operator can enable alongside the core {ref}`REST API <05_node-guide/01_node-rest-api:Node REST API>` for consumers that need direct access to binary data instead of JSON.

## gRPC Server

The node ships a `grpc-server` module (built alongside the core node in [node-scala](https://github.com/Decentral-America/node-scala/tree/main/grpc-server)) that exposes {ref}`blocks <02_decentralchain/10_binary-format:Block Binary Format>` and {ref}`transactions <02_decentralchain/10_binary-format:Transaction Binary Format>` directly in their protobuf-serialized binary format, rather than the JSON representation the REST API returns. This is the recommended way to consume chain data for a service that needs to process a large volume of blocks or transactions efficiently.

If you use your own node with the gRPC server enabled, you can send it a `SignedTransaction` object directly instead of composing a JSON transaction for the REST API's `POST /transactions/broadcast` method. See [`@decentralchain/protobuf-serialization`](https://www.npmjs.com/package/@decentralchain/protobuf-serialization) (published on npm today; the monorepo is renaming it to `protobuf-schemas`) for building and parsing these binary structures from JavaScript/TypeScript, or [Node gRPC API](../04_building-apps/05_node-grpc) for the typed client.

```{note}
Verified against node-scala v1.7.0 (`grpc-server/src/main/resources/application.conf`).
```

The module listens on two ports:

| Setting | Default | Purpose |
|---|---|---|
| `dcc.grpc.port` | `6870` | AccountsApi, AssetsApi, BlockchainApi, BlocksApi, TransactionsApi |
| `dcc.blockchain-updates.grpc-port` | `6881` | BlockchainUpdates — a real-time stream of block-level events |
| `dcc.grpc.host` | `localhost` | Interface the main gRPC service binds to |
| `dcc.grpc.worker-threads` | `4` | Worker threads for the gRPC service |
| `dcc.blockchain-updates.min-keep-alive` | `5m` | Minimum time a BlockchainUpdates subscription is kept alive |

The `grpc-server` module is not a separate process: it is an in-process node extension. Put its JARs on the node's classpath (the Docker image loads extensions from `lib/plugins/`) and enable it in the node config with `dcc.extensions = [com.decentralchain.api.grpc.GRPCServerExtension]` (commented out in the node's default `application.conf`). Enabling it is a deployment decision for the node operator, not a REST API toggle.