# Dart on the Server and the Command Line — Dart

Source: https://www.skillbyai.com/en/dart/p-server

> Build CLIs and HTTP servers in Dart, with JSON serialisation.

## Beyond mobile apps

Dart is a capable language for **command-line tools** and **backend services**, especially for teams already using Flutter who want to share models and validation code. For CLIs, **`package:args`** parses flags and subcommands, `dart:io` handles files, processes and stdin/stdout, and `dart compile exe` produces a single binary. For HTTP servers, **`package:shelf`** provides composable handlers and middleware with routing via `shelf_router`, and frameworks such as **Dart Frog** and **Serverpod** offer more structure, code generation and full-stack features. Server code uses the same async model: each request handler returns a `Future<Response>`, and multiple isolates can serve requests on several cores. For **JSON**, small projects map manually with `fromJson`/`toJson`, while larger ones use **`json_serializable`** (annotations plus `build_runner`) or **`freezed`** (immutable data classes with unions). Deploy native executables in small containers on Cloud Run, Kubernetes or any VM.

## A small shelf API

Routing, JSON responses and logging middleware.

```dart
import 'dart:convert';
import 'dart:io';

import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart' as io;
import 'package:shelf_router/shelf_router.dart';

final _orders = <String, Map<String, Object>>{
  'o-1': {'id': 'o-1', 'status': 'paid', 'total_paise': 49900},
};

Response _json(Object body, {int status = 200}) => Response(
      status,
      body: jsonEncode(body),
      headers: {'content-type': 'application/json'},
    );

Future<void> main() async {
  final router = Router()
    ..get('/health', (Request _) => _json({'status': 'ok'}))
    ..get('/orders/<id>', (Request request, String id) {
      final order = _orders[id];
      return order == null ? _json({'error': 'Not found'}, status: 404) : _json(order);
    });

  final handler = const Pipeline().addMiddleware(logRequests()).addHandler(router.call);
  final port = int.parse(Platform.environment['PORT'] ?? '8080');
  final server = await io.serve(handler, InternetAddress.anyIPv4, port);
  print('Listening on ${server.address.host}:${server.port}');
}
```

## One toolbox for the whole house

Using Dart on both the app and the server is like using one set of tools for every room: the same measurements (models), the same screwdrivers (validation code), and fewer chances of parts not fitting together.

**Quiz:** Which package provides composable HTTP handlers and middleware for Dart servers?

- [ ] package:args
- [x] package:shelf
- [ ] package:test
- [ ] package:lints

*Answer:* package:shelf. shelf is the foundational package for HTTP servers in Dart.