# centrifuge 0.8.0

Dart client to communicate with Centrifuge and Centrifugo from Flutter and VM over dart:io WebSocket





## Installing
```
export PUB_HOSTED_URL=https://pub.mirror.p-hatan.ir
flutter pub add 'centrifuge:0.8.0'
```
Published: 2021-11-19T13:44:41.383440Z
Expected archive SHA-256: 5ac2b57eb41061658952226aa4a82c3c923b8387fe1be4813a93bc1673b7620a

Available in cache; verification: upstream_checksum
## Direct dependencies
- fixnum: ^1.0.0
- meta: ^1.3.0
- protobuf: ^2.0.0

## Package README (untrusted upstream documentation)
[![Build Status](https://travis-ci.org/centrifugal/centrifuge-dart.svg?branch=master)](https://travis-ci.org/centrifugal/centrifuge-dart)
[![Coverage Status](https://coveralls.io/repos/github/centrifugal/centrifuge-dart/badge.svg?branch=master)](https://coveralls.io/github/centrifugal/centrifuge-dart?branch=master)

This repo contains a Dart connector library to communicate with Centrifugo server or a server based on Centrifuge library for Go language. This client uses WebSocket transport with binary Protobuf protocol format for Centrifuge protocol message encoding. See feature matrix below to find out which protocol features are supported here at the moment.

## Example

* `example\flutter_app` simple chat application
* `example\chat_app` one more chat example
* `example\console` simple console application
* `example\console_server_subs` demonstrates working with server-side subscriptions

## Usage

Create a client instance:

```dart
import 'package:centrifuge/centrifuge.dart' as centrifuge;

final client = centrifuge.createClient("ws://localhost:8000/connection/websocket?format=protobuf");
```

**Note that using** `?format=protobuf` **is required for Centrifugo < v3 and can be skipped for later versions**.

Centrifuge-dart uses binary Protobuf protocol internally but nothing stops you from sending JSON-encoded data over it. Our examples demonstrate this.

Connect to a server:

```dart
await client.connect();
```

To handle connect and disconnect events you can listen to `connectStream` and `disconnectStream`:

```dart
client.connectStream.listen(onEvent);
client.disconnectStream.listen(onEvent);
await client.connect();
```

Connect and disconnect events can happen many times throughout client lifetime.

Subscribe to a channel:

```dart
final subscription = client.getSubscription(channel);

subscription.publishStream.listen(onEvent);
subscription.joinStream.listen(onEvent);  
subscription.leaveStream.listen(onEvent);
subscription.subscribeSuccessStream.listen(onEvent);
subscription.subscribeErrorStream.listen(onEvent);
subscription.unsubscribeStream.listen(onEvent);

await subscription.subscribe();
```

Publish to a channel:

```dart
final data = utf8.encode(jsonEncode({'input': message}));
await subscription.publish(data);
```

When using server-side subscriptions you don't need to create Subscription instances, just set appropriate event handlers on `Client` instance:

```dart
client.connectStream.listen(onEvent);
client.disconnectStream.listen(onEvent);
client.subscribeStream.listen(onEvent);
client.publishStream.listen(onEvent);
await client.connect();
```

## Usage in background

When mobile application goes to background there are many OS-specific limitations for established persistent connections. Thus in most cases you need to disconnect from a server when app moves to background and connect again when app goes to foreground.

## Feature matrix

- [ ] connect to server using JSON protocol format
- [x] connect to server using Protobuf protocol format
- [x] connect with token (JWT)
- [x] connect with custom header
- [x] automatic reconnect in case of errors, network problems etc
- [x] exponential backoff for reconnect
- [x] connect and disconnect events
- [x] handle disconnect reason
- [x] subscribe on channel and handle asynchronous Publications
- [x] handle Join and Leave messages
- [x] handle Unsubscribe notifications
- [x] reconnect on subscribe timeout
- [x] publish method of Subscription
- [x] unsubscribe method of Subscription
- [x] presence method of Subscription
- [x] presence stats method of Subscription
- [x] history method of Subscription
- [x] top-level publish method
- [x] top-level presence method
- [x] top-level presence stats method
- [x] top-level history method
- [x] send asynchronous messages to server
- [x] handle asynchronous messages from server
- [x] send RPC commands
- [x] subscribe to private channels with token (JWT)
- [ ] connection JWT refresh
- [ ] private channel subscription token (JWT) refresh
- [ ] handle connection expired error
- [ ] handle subscription expired error
- [x] ping/pong to find broken connection
- [ ] message recovery mechanism for client-side subscriptions
- [x] server-side subscriptions
- [x] message recovery mechanism for server-side subscriptions
- [x] history stream pagination
- [ ] subscribe from the known StreamPosition

## Instructions for maintainers/contributors

### How to update protobuf definitions

1) Install `protoc` compiler
2) Install `protoc_plugin` https://pub.dev/packages/protoc_plugin (`dart pub global activate protoc_plugin`)
3) cd `lib/src/proto` and run `protoc --dart_out=. -I . client.proto`
4) cd to root and run `dartfmt -w lib/ test/` (install dartfmt with `dart pub global activate dart_style`)

### How to release

1) Update changelog
2) Bump version in `pubspec.yaml`, push, create new tag
3) `pub publish`

## Author

German Saprykin, saprykin.h@gmail.com

## Changelog
## [0.8.0]

Version 0.8.0 is the next iteration of `centrifuge-dart` development. It pushes client closer to other clients in the ecosystem. It also **contains several backwards incompatible changes**.

* Return Futures from `Client.connect`, `Client.disconnect`, `Subscription.subscribe`, `Subscription.unsubscribe` methods - addresses [#31](https://github.com/centrifugal/centrifuge-dart/issues/31).
* On initial connect fire `DisconnectEvent` on connection error - this makes behavior of `centrifuge-dart` similar to all other our clients - addresses [#56](https://github.com/centrifugal/centrifuge-dart/issues/56).
* Add client error stream to consume `ErrorEvent` - each transport failure will emit error to this stream - addresses [#56](https://github.com/centrifugal/centrifuge-dart/issues/56).
* Refactor subscription statuses - add `subscribing` and `error` statuses. This change is mostly internal should not affect working with Subscriptions.
* Do not call `UnsubscribeEvent` if subscription is not successfully subscribed (i.e. in `subscribed` state). This makes behavior of `centrifuge-dart` similar to all other our clients.
* Update disconnect reasons due to failed connection and calling `Client.Disconnect` method - make it more similar to all other connector libraries in ecosystem.
* Add default transport timeout (10 sec) – on connect and subscribe timeouts client will auto reconnect, calls like publish, history, rpc can now throw `TimeoutException`. Also - properly pass timeout to the transport (was not before!). Again – this makes client behave similarly to all other connectors.
* Add `presence` and `presenceStats` methods for Subscription and on client top level (for server-side subscriptions).
* Support `streamPosition` in `SubscribeSuccessEvent`.
* Support `streamPosition` in `ServerSubscribeEvent`.
* Support `data` in `ServerSubscribeEvent`.
* Implement `send` method to send async messages to a server.
* Fix deletion during iteration over map when working with server-side subscriptions.
* Better event String representations.
* Improvements and fixes in examples.

## [0.7.1]

* Add support for `data` in `SubscribeSuccessEvent`. This is a custom data which can be sent by a server towards client connection in subscribe result. Note that due to the bug in Centrifugo server this feature only works in Centrifugo >= v3.0.3.

## [0.7.0]

Update to work with Centrifuge >= v0.18.0 and Centrifugo v3.

**Breaking change** in server behavior. Client History API behavior changed in Centrifuge >= v0.18.0 and Centrifugo >= v3.0.0. When using history call it won't return all publications in a stream by default. See Centrifuge [v0.18.0 release notes](https://github.com/centrifugal/centrifuge/releases/tag/v0.18.0) or [Centrifugo v3 migration guide](https://centrifugal.dev/docs/getting-started/migration_v3) for more information and workaround on server-side.

* Protocol definitions updated to the latest version 
* History method now accepts optional `limit`, `since` and `reverse` arguments and returns `HistoryResult`
* RPC call now requires method name as first argument (you can pass empty string to mimic previous behavior)
* Publish now returns `PublishResult`
* When working with Centrifugo v3 or Centrifuge >= v0.18.0 it's now possible to avoid using `?format=protobuf` in connection URL. Client will negotiate Protobuf protocol with a server using WebSocket subprotocol mechanism (in request headers).

## [0.6.0]

Null safety migration

* library dependencies updated to null safe versions
* library code updated to support null safety in places where required

See issue [#47](https://github.com/centrifugal/centrifuge-dart/issues/47) and pull request [#48](https://github.com/centrifugal/centrifuge-dart/pull/48) for details.

## [0.5.1]
* Skip handling for events from server-side subscriptions resulted in null pointer dereference 

## [0.5.0]
* Update protobuf dependency to `^1.0.1`, thanks [@Holofox](https://github.com/Holofox)

## [0.4.1]
* Implement `removeSubscription` method, thanks [@tiamo](https://github.com/tiamo)

## [0.4.0]
* **Breaking changes** `connected` property removed

## [0.3.0]
* **Breaking changes** Changed API to avoid returning futures where they do not make sense – in `connect` and `subscribe` methods.
* Client now uses Websocket Ping/Pong frames to find broken connection
* Support for private channel subscription using `onPrivateSub` configuration callback function
* Fix several null pointer dereferences in edge cases, throw `ClientDisconnectedError` when there is an attempt to send protocol request over non-connected client.
* Fix examples where subscribe could happen before stream handlers set

## [0.2.0]
* **Breaking changes** Replaced subscribe method with getSubscription in Client. 
* Added reconnection.
* Added history method to Subscription. Thanks [vanelizarov](https://github.com/vanelizarov).
* Added rpc method.

## [0.1.0]
* Added authorization with JWT
* Added subscription to private channel with JWT

## [0.0.1]

* Initial release