nitro_server 1.0.0

Fast HTTP/1.1 and WebSocket server for Dart and Flutter, backed by a native multithreaded C++ engine over Nitro FFI, with trie routing and per-route timeouts.

nitro_server

HTTP/1.1 + HTTP/2 + WebSocket server for Dart and Flutter. Native C++ engine (libuv, via Nitro FFI) does accept / parse / route / write on every core; handlers run in Dart. Client library: nitro_http.

import 'package:nitro_server/nitro_server.dart';

Future<void> main() async {
  final server = await NitroServer.bind(); // 127.0.0.1, a free port
  await server.get('/hello', (_) => ResponseContext.text('hi 👋'));
  await server.get('/users/:id', (r) => ResponseContext.jsonBody({'id': r.param('id')}));
  await server.post('/echo', (r) => ResponseContext.bytes(r.body));
  print('listening on ${server.uri}');
}

Full entrypoint to copy: bin/server.dart (routes, OpenAPI, metrics, dashboard, drain, hot reload, env config).

• Install
• Build from source
• CLI
• Routes
• Request
• Response
• WebSocket
• Middleware
• Configuration
• Production
• Testing
• Hot reload
• Native library
• Exceptions
• Limits
• Performance
• Developing

Install

dart pub add nitro_server

• Released versions need no toolchain: the build hook downloads the prebuilt engine for your OS/arch and dart build cli bundles it.
• Prebuilts are self-contained (libuv, OpenSSL, brotli, nghttp2 linked in; libstdc++ too on Linux). Minimum hosts: Linux glibc 2.35 (Ubuntu 22.04, Debian 12 or newer), macOS 14, Windows 10 x64. Older hosts build from source.
• Downloads are verified against prebuilt_checksums.json (ships in the package). NITRO_SERVER_VERIFY_SIGSTORE=1 also runs cosign verify-blob. NITRO_SERVER_PREBUILT_BASE_URL points at a mirror.
• Do not dart compile exe a nitro_server program (no build hook, no engine). Use dart build cli or the CLI below.

Build from source

Needed for an unreleased version, an uncovered OS/arch, or NITRO_SERVER_BUILD_FROM_SOURCE=1. Requires a C++17 compiler, CMake ≥ 3.10, Dart ≥ 3.12.

Library	Enables	Required
libuv	reactor	yes
OpenSSL 3	TLS (and h2 over TLS)	optional, auto-detected
libbrotli	compress() br	optional, auto-detected
nghttp2	HTTP/2 (-DNITRO_SERVER_HTTP2=ON)	optional

brew install cmake pkg-config libuv openssl@3 brotli nghttp2                                  # macOS
sudo apt-get install -y cmake pkg-config libuv1-dev libssl-dev libbrotli-dev libnghttp2-dev   # Debian/Ubuntu
vcpkg install libuv openssl brotli nghttp2 --triplet x64-windows                              # Windows

cmake -S src -B build/lib -DCMAKE_BUILD_TYPE=Release -DNITRO_SERVER_HTTP2=ON
cmake --build build/lib --parallel

CMake options:

Option	Effect
-DNITRO_SERVER_HTTP2=ON	HTTP/2 (needs nghttp2)
-DNITRO_SERVER_STATIC_DEPS=ON	link libuv/OpenSSL/brotli/nghttp2 statically
-DNITRO_SERVER_WERROR=ON	warnings are errors
-DNITRO_SERVER_SANITIZE=address|thread|undefined	instrumented build
-DOPENSSL_ROOT_DIR=…	point at an OpenSSL

Windows: use the vcpkg toolchain file and let CMake pick the generator (or -G Ninja).

cmake -S src -B build/lib -DCMAKE_BUILD_TYPE=Release -DNITRO_SERVER_HTTP2=ON `
  -DCMAKE_TOOLCHAIN_FILE="$env:VCPKG_INSTALLATION_ROOT/scripts/buildsystems/vcpkg.cmake" `
  -DVCPKG_TARGET_TRIPLET=x64-windows
cmake --build build/lib --config Release --parallel

Runtime checks: brotliAvailable(); bind throws ServerTlsException when TLS is requested on an engine without OpenSSL.

CLI

dart run nitro_server:nitro <cmd> (or nitro <cmd> after dart pub global activate nitro_server).

Command	Does
serve	run bin/server.dart, JIT + hot reload
serve <entry>	another entrypoint
serve --aot	compile, then run
build	AOT bundle → build/<name>/bundle/bin/<name> (engine in bundle/lib/)
build --jit	kernel snapshot → build/<name>.dill
build -o <path>	output path
build --bundle-deps	copy native deps beside the exe

dart run nitro_server:nitro serve                 # dev
dart run nitro_server:nitro build                 # prod: ./build/server/bundle/bin/server
docker build -t myapp . && docker run -p 8080:8080 -e ADMIN_USER=ops -e ADMIN_PASSWORD=... myapp

Deploy recipes (Fly.io, Render, Railway, Cloud Run, Kubernetes, Netlify): doc/deployment.md.

Routes

Snippets run inside setup(NitroServer server) or after final server = await NitroServer.bind(const ServerConfig(port: 8080));. Handlers may be sync or async. await registrations.

await server.get('/users/:id', (r) => ResponseContext.text('user ${r.param('id')}'));
await server.post('/upload/*', (r) => ResponseContext.text('${r.body.length} bytes'),
    maxBodyBytes: 50 * 1024 * 1024);
await server.put('/items/:id', (r) => ResponseContext.jsonBody(r.jsonMap()));
await server.delete('/items/:id', (r) => ResponseContext.text('', status: 204));
await server.all('/ping', (_) => ResponseContext.text('pong'));

await server.route(HttpMethod.custom, '/items', (_) => ResponseContext.text('report'),
    customMethod: 'REPORT');
await server.get('/slow', (_) => ResponseContext.text('done'),
    timeout: const Duration(seconds: 5)); // 408 past it

final api = server.group('/api/v1');
await api.use(cors()); // before the group's routes
await api.get('/ping', (_) => ResponseContext.text('pong'));
final v2 = api.group('/v2');

server.notFoundHandler = (r) => ResponseContext.text('no ${r.path}', status: 404);
server.errorHandler = (e, r) => ResponseContext.text('oops: $e', status: 500);

await server.unroute(HttpMethod.get, '/slow');

Controller class:

class UserController extends Controller {
  UserController() : super(prefix: '/users', middleware: [cors()]);
  final _users = <String, Object?>{'42': 'Ada'};

  @override
  Future<void> register(RouteGroup on) async {
    await on.get('/', (_) => ResponseContext.jsonBody(_users));
    await on.get('/:id', getOne);
    await on.post('/', create);
  }

  ResponseContext getOne(RequestContext c) =>
      ResponseContext.jsonBody({c.param('id'): _users[c.param('id')]});

  ResponseContext create(RequestContext c) {
    final body = c.jsonMap();
    _users['${body['id']}'] = body['name'];
    return ResponseContext.jsonBody(body, status: 201);
  }
}

await server.mount(UserController());

Engine-served static responses (no handler, no middleware, no FFI):

await server.getStatic('/health', utf8.encode('ok'), contentType: 'text/plain');
await server.staticRoute(HttpMethod.get, '/version', utf8.encode('{"v":"1.0.0"}'),
    contentType: 'application/json', headers: {'cache-control': 'max-age=60'});

• Precedence: static segment > :param > *; method-specific > all; HEAD falls back to GET.
• Middleware order: server → group → route.
• Handler past timeout → 408. Throwing handler → 500 (or errorHandler).

Request

await server.post('/users/:id', (r) {
  r.method;                 // HttpMethod.post (r.customMethod for custom verbs)
  r.path;                   // '/users/42' (r.routePattern = '/users/:id')
  r.param('id');            // '42' (r.params)
  r.queryParam('page');     // r.queryParameters, r.queryParamAll, r.queryParametersAll
  r.header('x-request-id'); // first value, case-insensitive; r.headers: Map<String, List<String>>
  r.cookies['session'];
  r.clientIp;               // '' when unavailable
  r.body;                   // Uint8List
  r.text();
  final m = r.jsonMap();    // also jsonList(), json(), jsonAs<T>()
  return ResponseContext.jsonBody({'id': r.param('id'), 'got': m});
});

Multipart:

await server.post('/upload', (r) {
  final parts = r.multipart(); // FormatException unless multipart/form-data
  for (final p in parts) {
    if (p.isFile) {
      File('uploads/${p.filename}').writeAsBytesSync(p.bytes); // p.contentType
    } else {
      print('${p.name} = ${p.text()}');
    }
  }
  return ResponseContext.jsonBody({'parts': parts.length});
}, maxBodyBytes: 50 * 1024 * 1024);

Limits: maxParts 1000, maxPartHeaderBytes 8 KiB, boundary 1–70 chars; parts are views into r.body.

Streaming upload (HTTP/1.1):

await server.post('/ingest', (r) async {
  var total = 0;
  await for (final chunk in r.bodyStream!) {
    total += chunk.length;
  }
  return ResponseContext.text('received $total bytes');
}, streamBody: true); // r.body is empty, r.bodyStream is set

Response

All take status: and headers:.

ResponseContext.text('hi');                                      // text/plain; charset=utf-8
ResponseContext.text('<b>hi</b>', contentType: 'text/html');
ResponseContext.html('<h1>hi</h1>');
ResponseContext.jsonBody({'ok': true, 'n': [1, 2]});             // any JSON-encodable
ResponseContext.jsonMap({'ok': true});
ResponseContext.json('{"pre":"encoded"}');
ResponseContext.bytes(Uint8List(0), contentType: 'image/png');
ResponseContext.redirect('/login');                              // 302; status: 301/303/307/308
ResponseContext.file('report.pdf', contentType: 'application/pdf'); // engine-sent in chunks; offset:/length:
ResponseContext.stream(Stream.value(Uint8List(0)), contentType: 'text/csv'); // chunked
ResponseContext.text('created', status: 201, headers: {'location': '/items/7'});

Cookies and headers:

await server.get('/login', (_) => ResponseContext.text('ok')
    .withCookie(SetCookie('session', 'abc123',
        httpOnly: true, secure: true, sameSite: SameSite.lax,
        maxAge: const Duration(days: 7), path: '/'))
    .withHeader('cache-control', 'no-store'));

copyWith(status:, headers:) keeps a stream/file/cookies. A header or cookie with CR/LF/NUL is never sent: 500 + handlerError event.

Server-Sent Events:

await server.get('/events', (_) => ResponseContext.sse(
  Stream.periodic(const Duration(seconds: 1),
      (i) => SseEvent('tick $i', event: 'tick', id: '$i')).take(10),
));

SseEvent(data, {event, id, retry}), bufferSize: batches writes. Send something more often than streamIdleTimeout (5 min) or the stream is closed.

Problem details (RFC 7807):

await server.post('/orders', (r) {
  if (r.jsonMap()['email'] == null) {
    return ResponseContext.problem(
      title: 'Validation failed', status: 422, detail: 'email is required',
      type: 'https://example.com/errors/validation', extensions: {'field': 'email'},
    );
  }
  return ResponseContext.text('ok', status: 201);
});

Native JSON writer (encodes into the engine's buffer, no Dart string):

final kId = JsonToken('id'), kName = JsonToken('name'); // hoist interned keys

await server.get('/report', (_) => ResponseContext.jsonWriter((w) {
  w..beginObject()..key('ok')..writeBool(true)..key('rows')..beginArray();
  for (var i = 0; i < 3; i++) {
    w..beginObject()..keyToken(kId)..writeInt(i)..keyToken(kName)..writeString('row $i')..endObject();
  }
  w..endArray()..endObject();
}));

writeInt/Double/Num/String/Bool/Null, writeValue(any), writeRaw(fragment), keyToken/writeStringToken. The build callback is synchronous.

WebSocket

await server.ws('/chat', (session) async {
  session.protocol;                        // negotiated subprotocol or null
  session.handshake.header('x-user');      // the upgrade request
  await for (final m in session.messages) {
    if (m is WsText) session.sendText('echo: ${m.text}');   // returns queued bytes; -1 = closed
    if (m is WsBinary) session.sendBytes(m.bytes);
    if (session.bufferedBytes > 1 << 20) await session.close(1009);
  }
  // returning or throwing closes the session; session.closeCode = peer's code
}, protocols: ['chat.v1'], middleware: [bearerAuth((t) => t == 'secret')]);

• WsSession: handshake, messages (WsText | WsBinary), sendText, sendBytes, bufferedBytes, compressed, protocol, closeCode, close([code = 1000]).
• Engine does the handshake, ping/pong, close codes, permessage-deflate.
• Server-global middleware does not run on WS routes. Use ws(middleware: [...]): a rejection closes with 4000 + status (401 → 4401), 1008 for a non-4xx, 1011 if the middleware throws.
• group.ws(...) prepends the group's use list.

Middleware

await server.use(accessLog());                       // json: true for JSON lines
await server.use(requestId());                       // x-request-id in/out
await server.use(cors(allowOrigin: 'https://example.com', allowCredentials: true));
await server.use(compress(minBytes: 1024, level: 1, brotliQuality: 4));
await server.use(rateLimit(maxRequests: 100, window: const Duration(minutes: 1)));
await server.use(rateLimit(maxRequests: 100, trustedProxies: ['10.0.0.0/8'])); // believe X-Forwarded-For from these peers only
await server.use(bearerAuth((token) => token == 'secret', realm: 'api'));
await server.use(apiKeyAuth((key) => key == 'k', headerName: 'x-api-key'));
await server.use(basicAuth((user, pass) => user == 'admin' && pass == 'pw'));
await server.use(originPolicy(['https://app.example.com'])); // 403 unless Origin matches; also gates ws() handshakes (4403)

// Static files: a handler on a wildcard route
await server.get('/assets/*', staticFiles('web', maxAge: const Duration(hours: 1)));

• staticFiles: etag, 304, byte ranges, index.html; .., encoded dots, NUL, symlinks out of the root and dotfiles are 404 (dotfiles: true, followSymlinks: false to change).
• Scope: server.use (server-wide), group.use (before its routes), middleware: [...] per route or ws(), controllers.
• cors() refuses * with credentials. rateLimit keys on the socket peer unless trustedProxies names the peer.

Custom middleware:

Middleware timing() => (request, next) async {
  final sw = Stopwatch()..start();
  final res = await next(request);
  return res.withHeader('x-elapsed-ms', '${sw.elapsedMilliseconds}');
};

final Middleware requireAdmin = (request, next) => request.header('x-role') == 'admin'
    ? next(request)
    : ResponseContext.text('forbidden', status: 403);

await server.use(timing());
await server.get('/admin', (_) => ResponseContext.text('hi'), middleware: [requireAdmin]);

Shared rate-limit store (default store is per isolate, bounded to maxKeys):

class CountingStore implements RateLimitStore { // swap the map for Redis INCR+EXPIRE
  final _hits = <String, RateLimitHit>{};
  @override
  RateLimitHit hit(String key, Duration window) {
    final now = DateTime.now();
    final prev = _hits[key];
    return _hits[key] = (prev == null || now.isAfter(prev.resetAt))
        ? RateLimitHit(count: 1, resetAt: now.add(window))
        : RateLimitHit(count: prev.count + 1, resetAt: prev.resetAt);
  }
}

await server.use(rateLimit(
  maxRequests: 100,
  store: CountingStore(),
  keyExtractor: (r) => r.header('x-api-key') ?? r.clientIp,
  onLimit: (retryAfter) => ResponseContext.problem(title: 'Too many requests', status: 429),
));

JSON body validation:

final userSchema = ApiSchema.object({
  'name': ApiSchema.string(),
  'email': ApiSchema.string(format: 'email'),
  'age': ApiSchema.integer(nullable: true),
}, required: ['name', 'email']);

await server.post('/users', (r) => ResponseContext.jsonBody(r.jsonMap(), status: 201),
    middleware: [validateJsonBody(userSchema)]); // 400 bad JSON, 422 schema failure

ApiSchema.string/integer/number/boolean/object/array/ref, schema.validate(v), toJson(); maxErrors (100) caps the 422 list.

Configuration

Future<void> setup(NitroServer server) async {
  await server.get('/report', (_) => ResponseContext.jsonBody({'ok': true}));
}

final server = await NitroServer.bind(
  const ServerConfig(port: 8080, isolates: 0),
  setup, // required when isolates != 1
);

ServerConfig	default	meaning
host, port, backlog	127.0.0.1, 0, 128	bind address (IPv6 and :: ok), port (0 = free), listen backlog
isolates	1	handler isolates; 0 = one per core (needs setup); raise for CPU-bound handlers
workerThreads	0	libuv loop threads; 0 = one per core
defaultTimeout	30 s	handler deadline, 408 past it and the request is released; Duration.zero disables
keepAliveTimeout, maxRequestsPerConnection	5 s, 100	idle deadline between requests; requests per connection (0 = unbounded)
headerTimeout	idle timeout	absolute deadline from the first byte of a request head / TLS handshake
bodyTimeout	keep-alive timeout	stall window for a request body still arriving: 408
writeTimeout	30 s	stalled write drops the connection (+ clientError); cannot be disabled
streamIdleTimeout	5 min	streaming response with no write for this long is closed (+ clientError); Duration.zero disables
maxConnectionAge	0 = unbounded	hard connection lifetime (HTTP/1.1 after its answer, WS 1001, h2 GOAWAY)
wsIdleTimeout	60 s	WS pinged at half, closed 1001 at the full window; Duration.zero disables
maxBodyBytes	10 MiB	request body cap, 413; per route via maxBodyBytes:
maxBufferedBodyBytes	64 MiB	HTTP/2: request-body bytes one session holds across streams; over the remainder 503, never fits 413; ≥ maxBodyBytes
maxConnections, maxConnectionsPerIp	0 = unlimited	refused at accept; per-IP follows the PROXY client when proxyProtocol
maxInFlightRequests	0 = unlimited	dispatched-not-answered budget; 503 + Retry-After: 1 past it
wsMaxBufferBytes, wsCompression	1 MiB, true	WS queue bound each direction (1009 past it); permessage-deflate
streamMaxBufferBytes	4 MiB	unsent bytes a streaming response may queue; connection dropped past it; 0 = unlimited
exposeErrorDetails	false	true puts the error text in the 500 body (dev only); details always go to events
proxyProtocol	false	expect a HAProxy PROXY v1/v2 header first; its address becomes clientIp
responseTiming	true	Server-Timing: app;dur=<ms> on handler answers
tls	none	TlsConfig(certPem:/keyPem: or certFile:/keyFile:); minVersion, ciphers, cipherSuites, clientCaPem:/clientCaFile: (mutual TLS)
protocol	HttpProtocol.http2	http1, http2 (ALPN h2 + h2c, falls back to 1.1), http3 (reserved)

Memory per connection: one body (h1) or maxBufferedBodyBytes (h2) + streamMaxBufferBytes / wsMaxBufferBytes + 64 KiB parse buffer. Multiply by maxConnections for the server bound.

config.copyWith(...); bind runs config.validate() (ArgumentError).

Environment:

final server = await NitroServer.bind(ServerConfig.fromEnv(Platform.environment), setup);
// HOST PORT BACKLOG ISOLATES WORKER_THREADS MAX_BODY_BYTES MAX_BUFFERED_BODY_BYTES MAX_CONNECTIONS
// MAX_CONNECTIONS_PER_IP MAX_REQUESTS_PER_CONNECTION MAX_IN_FLIGHT_REQUESTS MAX_CONNECTION_AGE_MS
// KEEP_ALIVE_TIMEOUT_MS DEFAULT_TIMEOUT_MS HEADER_TIMEOUT_MS WRITE_TIMEOUT_MS BODY_TIMEOUT_MS
// STREAM_IDLE_TIMEOUT_MS STREAM_MAX_BUFFER_BYTES WS_IDLE_TIMEOUT_MS WS_MAX_BUFFER_BYTES
// WS_COMPRESSION RESPONSE_TIMING EXPOSE_ERROR_DETAILS PROXY_PROTOCOL HTTP_PROTOCOL
// TLS_CERT_FILE+TLS_KEY_FILE | TLS_CERT_PEM+TLS_KEY_PEM TLS_MIN_VERSION (1.2|1.3)
// TLS_CIPHERS TLS_CIPHER_SUITES TLS_CLIENT_CA_FILE | TLS_CLIENT_CA_PEM
// A value that does not parse throws FormatException.

TLS:

final server = await NitroServer.bind(
  const ServerConfig(port: 8443, tls: TlsConfig(certFile: 'cert.pem', keyFile: 'key.pem')),
  setup,
);
server.reloadTls(const TlsConfig(certFile: 'renewed.pem', keyFile: 'renewed.key')); // no downtime

Production

Observability:

var dbReady = false;
await serveObservability(server,
    ready: () => dbReady,   // /readyz 503 while false
    middleware: [basicAuth((u, p) => u == 'ops' && p == env['OPS_PW'])], // guards /metrics + dashboard
    maxDashboardViewers: 16,
    dashboardPath: null,    // drop the dashboard
    prefix: 'myapp');
// GET /healthz   200 while serving
// GET /readyz    503 while draining or when a helper isolate died
// GET /metrics   Prometheus text (requests, errors, in-flight, responses_total{class}, connections,
//                event_loop_lag_seconds, helper_isolates_alive, per-route latency summary)
// GET /dashboard live HTML

• Aggregates across isolates: await server.aggregatedMetrics(); server.metrics is this isolate.
• prometheusFormat(m) / metricsJson(m) are renderers.
• Put middleware: on a public listener; /metrics reveals route names.

OpenAPI + Swagger UI:

await serveOpenApi(server, title: 'My API'); // spec from routes, Swagger UI at /docs

final api = OpenApi(server, title: 'My API',
    securitySchemes: {'bearer': bearerScheme(bearerFormat: 'JWT')});

await api.get('/search', (r) => ResponseContext.jsonBody({'q': r.queryParam('q')}),
    doc: const OpenApiOperation(
      summary: 'Search',
      params: [OpenApiParam.query('q', required: true), OpenApiParam.header('X-Request-Id')],
      responseExample: {'total': 0},
    ));

await api.post('/users', (r) => ResponseContext.jsonBody(r.jsonMap(), status: 201),
    doc: const OpenApiOperation(
      requestExample: {'name': 'Ada', 'email': '[e-mail]'},
      successStatus: 201,
      extraResponses: {'400': OpenApiResponse('Invalid body')},
    ));

await api.post('/upload', (r) => ResponseContext.jsonBody({'parts': r.multipart().length}),
    doc: const OpenApiOperation(requestBodyDoc: OpenApiRequestBody.multipart(schema: {
      'type': 'object', 'properties': {'file': {'type': 'string', 'format': 'binary'}},
    })));

await api.get('/me', (_) => ResponseContext.jsonBody({'ok': true}),
    middleware: [bearerAuth((t) => t == 'secret')],
    doc: const OpenApiOperation(requiresAuth: ['bearer']));

await api.serve(middleware: [requireAdmin]); // /openapi.json + /docs

• OpenApiParam.query/.header/.cookie; OpenApiRequestBody.json/.form/.multipart/.text/.binary.
• Schemes: bearerScheme(), apiKeyScheme(), basicScheme(), oauth2Scheme(), openIdConnectScheme().
• Swagger UI pinned (swaggerUiPinnedVersion 5.17.14) with SRI + CSP.

Shutdown:

final shutdown = shutdownOnSignals(server,
    drain: const Duration(seconds: 15), onSignal: (s) => print('$s: draining'));
await server.onClose;
// or: await server.close(drain: const Duration(seconds: 15));

Events:

server.events.listen((e) => print('${e.kind.name} #${e.requestId}: ${e.message}'));
// started, stopped, handlerTimeout, clientError, clientDisconnect, notice (helper isolate
// died, ...), handlerError (handler threw or produced an unsendable response; message has
// verb, path, error, stack)

Banner:

print(serverBanner(
  title: 'my-api', version: '1.0.0', uri: server.uri,
  isolates: server.isolates, pid: pid, routes: server.routes,
  links: {'docs': '/docs', 'metrics': '/metrics'},
  facts: ['hot reload off'], logo: nitroServerAsciiLogo,
  color: stdout.supportsAnsiEscapes,
));

Testing

package:nitro_server/testing.dart: the real runner in memory, no sockets, no native library.

import 'package:nitro_server/nitro_server.dart';
import 'package:nitro_server/testing.dart';
import 'package:test/test.dart';

void main() {
  test('routes and websocket', () async {
    final client = await NitroTestClient.start();
    final s = client.server;
    await s.get('/users/:id', (r) => ResponseContext.text('u${r.param('id')}'));
    await s.post('/echo', (r) => ResponseContext.jsonBody(r.jsonMap()));
    await s.ws('/ws', (session) async {
      await for (final m in session.messages) {
        if (m is WsText) session.sendText('echo: ${m.text}');
      }
    });

    expect((await client.get('/users/42')).text(), 'u42');

    final posted = await client.post('/echo',
        body: {'a': 1}, headers: {'content-type': 'application/json'});
    expect(posted.status, 200);
    expect(posted.json(), {'a': 1});

    final ws = await client.ws('/ws');
    ws.sendText('hi');
    expect((await ws.messages.first).text, 'echo: hi');
    await ws.close();

    await client.close();
  });
}

Not enforced in memory: route timeouts, maxBodyBytes; clientIp is '', port is 0.

Hot reload

import 'package:nitro_server/hot_reload.dart';
import 'package:nitro_server/nitro_server.dart';

Future<void> setup(NitroServer server) async {
  await server.get('/hello', (_) => ResponseContext.text('hi'));
}

Future<void> main() async {
  final server = await NitroServer.bind(const ServerConfig(port: 8080), setup);
  try {
    await enableHotReload(server, log: print); // watch: ['lib', 'bin']
  } catch (_) {
    // AOT or no VM service
  }
  await server.onClose;
}

• server.reload([setup]) swaps the whole routing surface on the live socket.
• Needs hotreloader in dev_dependencies and dart run --enable-vm-service; throws under AOT.
• setup must be a top-level or static function.

Native library

Search order: explicit path → NITRO_SERVER_DYLIB → beside the executable (lib/, ../lib/) → .dart_tool/lib → build/lib → build/.

loadNitroServerNative(path: '/opt/libs/libnitro_server.so');
final server = await NitroServer.bindWith(port: 8080, dylibPath: '/opt/libs/libnitro_server.so');

Exceptions

try {
  await NitroServer.bind(const ServerConfig(port: 80));
} on ServerBindException catch (e) {
  print('cannot bind: ${e.message}');
} on ServerTlsException catch (e) {
  print('TLS unavailable: ${e.message}');
}

• NitroServerException subclasses: ServerBindException, ServerTlsException, ServerAlreadyRunningException, ServerNotRunningException, RouteNotFoundException, ServerBadRequestException, HandlerTimeoutException, ServerUnknownException.
• ArgumentError: bad pattern/prefix, isolates > 1 without setup, config.validate(), cors() wildcard + credentials, rateLimit limits.
• StateError: reload without a setup, missing dylib, helper isolate that never starts. FormatException: json*(), multipart(), fromEnv.
• A throwing handler answers 500 internal server error; details go to events (handlerError).

Limits

• Platforms: iOS (foreground), Android (foreground service), macOS, Linux, Windows. No web.
• HTTP/3 not implemented; terminate it at a proxy.
• TLS/brotli are build-time (prebuilts have both).
• Not serverless: a persistent process.
• metrics and the default rate-limit store are per isolate (use a shared RateLimitStore).
• getStatic/staticRoute answers never reach Dart: no auth, no logging, no rate limit.
• HTTP/2 request bodies are buffered (up to the route's maxBodyBytes), not streamed; streamBody is HTTP/1.1 only.
• Client addresses come from the socket; X-Forwarded-For only with trustedProxies; behind an L4 balancer use proxyProtocol.
• close(drain:): new connections get 503, h2 gets GOAWAY; a connection still in the kernel backlog at final close may be reset.
• Helper isolates: one that misses NitroServer.helperTimeout (10 s) or dies is killed, detached, reported (notice, /readyz 503).

Performance

benchmark/blackbox/run.sh: every framework an opaque HTTP server, oha at 64 keep-alive connections, 3 server cores each, load generator on other cores, medians of interleaved reps, responses byte-validated. Linux container on Apple Silicon, nitro 0.8.0, 2026-10-22, final engine, 5 reps. nitro = _dylib build; @Native within 4% on every route. Hardening cost vs the pre-audit tree, same run (--base): 1–4% on light routes (widest -5.7% on /q?a=1&b=two), none on /work.

framework	configuration
nitro	isolates: 3
go	net/http, GOMAXPROCS=3
node	http + cluster, 3 workers
dart:io	HttpServer, 3 isolates (SO_REUSEPORT)
shelf	shelf_io.serve, 3 isolates

Throughput (req/s, median; bold = fastest):

route	nitro	go	node	dart:io	shelf
/json (light I/O)¹	166k	220k	150k	71k	61k
/work (encode 200 JSON records)²	46k	17k	54k	8.6k	8.4k
/echo (4 KB body)	99k	80k	110k	64k	46k
/static (engine fast-path)³	455k	223k	148k	75k	61k

¹ /hello, /q, /users, /files, /mw are within ~5% of /json. ² per-request encode on every framework. ³ nitro answers from the engine (getStatic); the others run a handler.

Tail latency, /work (ms, median; bold = best p99):

framework	p50	p90	p99	p50:p99
node	1.05	1.52	3.59	3.4×
nitro	1.21	2.56	4.11	3.4×
dart:io	7.27	9.18	11.36	1.6×
shelf	7.39	10.33	13.54	1.8×
go	0.93	10.89	21.18	22.7×

Peak RSS (whole workload; bold = lowest):

framework	nitro	go	node	dart:io	shelf
peak RSS	151 MB	12 MB	391 MB	53 MB	51 MB

nitro = 3 isolate heaps + the engine; a single-isolate server is ~30–50 MB. Full report of this run: benchmark/blackbox/REPORT.md. A/B of two nitro builds: run.sh --base <git-ref> (see benchmark/BENCHMARKING.md).

Developing

cmake -S src -B build/lib -DCMAKE_BUILD_TYPE=Release -DNITRO_SERVER_BUILD_TESTS=ON -DNITRO_SERVER_HTTP2=ON
cmake --build build/lib --parallel
./build/lib/nitro_server_tests/nitro_server_engine_tests   # C++ suite
dart test                                                  # Dart suites
bash tool/coverage.sh                                      # Dart 100% line gate
bash tool/cpp_coverage.sh 90                               # engine line gate
bash tool/fuzz.sh 60                                       # libFuzzer targets
run-clang-tidy -p build/tidy src/engine/*.cpp              # .clang-tidy

• Bridge spec: lib/src/nitro_server.native.dart; regenerate with dart run build_runner build + nitrogen link. Never edit *.g.*.
• In this repository the hook stages build/lib/libnitro_server.* (your cmake build) ahead of any prebuilt, so dart test always runs the engine in the tree; remove build/lib to exercise the download path.
• CI (ci.yml): suites, both coverage gates, ASan/TSan (leak detection on Linux), fuzz smoke, clang-tidy, Docker build + /readyz + Trivy, h2spec (floor 136/146), Autobahn (0 FAILED). soak.yml: nightly 10-minute memory soak. release.yml: suites → prebuilts with Sigstore provenance, keyless cosign bundle, SPDX SBOM → verify job locks and re-verifies them (tool/update_prebuilt_lock.sh, tool/verify_prebuilt_lock.dart); commit the lock before dart pub publish.
• README code is verified: every dart block above is copied verbatim into test/readme/*.dart, compiled by dart analyze/dart test, and test/readme_snippets_test.dart fails if a README line is missing there.