whisper_websocket_client_dart

A WebSocket client for Whisper messaging server.

Installation

Add the following dependency to your pubspec.yaml

whisper_websocket_client_dart:
    git:
      url: https://github.com/jsfraz/whisper_websocket_client_dart.git

Usage

import 'package:whisper_websocket_client_dart/ws_client.dart';

var wsClient = WsClient('ws://localhost:8080/ws', onReceived: (wsResponse) {
    // TODO handle server response
});
await wsClient.connect(accessToken, Duration(seconds: 5));

await Future.delayed(Duration(seconds: 5));
wsClient.disconnect();

For more detailed example see test/ws_client_test.dart.

Sending media (images, gifs, videos, voice)

Media files are transferred over HTTP, not over the WebSocket. The file is encrypted locally and uploaded as ciphertext; only a small encrypted reference to it travels inside a normal private message, so the server never learns anything about the media (zero-knowledge). The server stores the file on disk with a TTL and deletes it after the recipient downloads it once (or when the TTL expires).

Sender flow:

1. Encrypt the media file locally and upload the ciphertext with MediaApi.uploadMedia(receiverId, file) from whisper_openapi_client_dart, which returns the media id.
2. Build a MediaReference(id, key, type, size, ...) describing the upload (including the symmetric key needed to decrypt it).
3. Serialize the reference (mediaReference.toJson()), encrypt it the same way text messages are encrypted, and send it as the content of a NewPrivateMessage.

Recipient flow:

1. Decrypt the received message content and parse it with MediaReference.fromJson(...).
2. Download the ciphertext via MediaApi.downloadMedia(mediaReference.mediaId).
3. Decrypt it locally using mediaReference.key.
4. Only after the file is successfully downloaded, decrypted and persisted, call MediaApi.confirmMediaDownload(mediaReference.mediaId) to delete it from the server. The download is retriable until confirmed; if the client never confirms, the file is removed once its server-side TTL expires.

Dependencies

• web_socket_channel
  • provides WebSocket support for Dart

Dev dependencies

• lints
  • lint rules for Dart code analysis
• test
  • testing framework
• dotenv
  • environment variables from .env files
• pointycastle
  • used for cryptography
• basic_utils
  • used for cryptography
• dart_jsonwebtoken
  • used for JWT token handling
• whisper_openapi_client_dart
  • used for API communication with Whisper server