GitHub - geograms/i2p-dart: Pure-Dart I2P node: decentralized, NAT-traversing, content-addressed file sharing — no native binaries, no router install, no config.

A pure-Dart I2P node. Decentralized, NAT-traversing, content-addressed file sharing — with no native binaries, no separate router install, and no router configuration. The full I2P client runs in plain Dart, so it works in any Dart or Flutter application (desktop, mobile, server) by just adding a package.

This package was extracted from the Aurora project so it can be reused as a standalone library.

What it does

NTCP2 transport — Noise XK handshake + data phase against the live network.
Tunnels — builds inbound and outbound tunnels (ECIES short build records), with gateway diversity, rotation and health scoring.
netDB — reseeds over HTTPS (multi-operator), looks up and publishes LeaseSet2 records to the floodfill DHT.
Repliable signed datagrams — Ed25519-signed GET/DAT by sha256.
Content discovery — an IPFS-style provider DHT (PROVIDE / FINDPROV): find a blob by its sha256 without knowing which device holds it.
Swarm — a BitTorrent-style piece swarm so large files download collectively from many devices in parallel, each piece sha256-verified.
Background isolate — the node runs off the UI isolate, with cooperative pause() / resume() for CPU / battery governors.

Everything is content-addressed by sha256: you serve and fetch opaque blobs by hash. Mapping hashes to your app's files/messages is left to you.

Install

dependencies:
  i2p:
    git:
      url: https://github.com/geograms/i2p-dart.git

Quick start

import 'dart:typed_data';
import 'package:i2p/i2p.dart';

// Back the node with your own storage (keyed by sha256, base64url, no padding).
class MyStore implements I2pContentStore {
  @override
  Future<Uint8List?> get(String sha256B64u) async { /* return bytes or null */ }
  @override
  Future<void> put(Uint8List bytes, String ext) async { /* persist bytes */ }
}

final i2p = I2pService(store: MyStore(), log: print);

await i2p.ensureStarted();          // reseed + build tunnels (idempotent)
print('reachable at ${i2p.b32}.b32.i2p');

// Make a blob discoverable by its hash:
await i2p.announce(sha256Bytes);

// Fetch by hash from anyone on the network who has it:
await i2p.discover(sha256Bytes, 'jpg');

// Or fetch directly from a known peer's address:
await i2p.fetchByB32('<52chars>.b32.i2p', sha256Bytes, 'jpg');

i2p.pause();   // under battery / CPU pressure — cheap to resume()
await i2p.resume();
i2p.stop();

If you don't want to implement the interface, use the callback form:

final i2p = I2pService(
  store: I2pCallbackStore(
    onGet: (k) async => myMap[k],
    onPut: (bytes, ext) async => myMap[hashOf(bytes)] = bytes,
  ),
);

A runnable end-to-end demo is in example/i2p_example.dart.

API surface

Most apps only need I2pService (the facade) and I2pContentStore (your storage hook). For lower-level control the package also exports:

I2pWorker / I2pWorkerConfig — the isolate runner you can drive directly.
I2pNode — the node itself (transport, tunnels, datagrams, swarm), if you want to run it on your own isolate or embed it.
RouterInfo, parseRouterInfo, reseed, reseedRouters — netDB helpers.

Notes & limitations

Network selection: I2pService(netId: 2) is the live public net. Use an isolated netId to point at a private testnet (e.g. a local i2pd).
Datagrams are signed but not yet encrypted (garlic ECIES for payloads is not implemented), so transit routers can read content. Add confidentiality before relying on it for private data.
2-hop inbound tunnels are opt-in (hops) and not yet established on the live net; the default 1-hop path is the proven one. 1-hop forwarding is probabilistic, so the node leans on gateway diversity + retry + persistence.
Mobile NAT: phones behind carrier CGNAT may fail the data plane in some conditions; see the Aurora project notes for the current state.

What it does

Install

Quick start

API surface

Notes & limitations

License