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https://github.com/felangel/web_socket_client

A simple WebSocket client for Dart which includes automatic reconnection logic.
https://github.com/felangel/web_socket_client

dart dart-package web-socket websocket websocket-client

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A simple WebSocket client for Dart which includes automatic reconnection logic.

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# WebSocket Client



[![build][build_badge]][build_link] [![coverage][coverage_badge]][build_link]

[![pub package][pub_badge]][pub_link]

[![style: very good analysis][very_good_analysis_badge]][very_good_analysis_link]

[![License: MIT][license_badge]][license_link]



A simple `WebSocket` client for Dart which includes automatic reconnection

logic.



## Quick Start 🚀



```dart

// Create a WebSocket client.

final socket = WebSocket(Uri.parse('ws://localhost:8080'));



// Listen to messages from the server.

socket.messages.listen((message) {

  // Handle incoming messages.

});



// Send a message to the server.

socket.send('ping');



// Close the connection.

socket.close();

```



## Establishing a Connection 🔌



The `WebSocket` client will attempt to establish a connection immediately upon

initialization. By default, a timeout will occur if establishing a connection

exceeds 60 seconds but a custom `timeout` duration can be provided:



```dart

final uri = Uri.parse('ws://localhost:8080');



// Trigger a timeout if establishing a connection exceeds 10s.

final timeout = Duration(seconds: 10);

final socket = WebSocket(uri, timeout: timeout);

```



## Reconnecting 🔄



If the `WebSocket` client is not able to establish a connection, it will

automatically attempt to reconnect using the provided `Backoff` strategy. By

default, a `BinaryExponentialBackoff` is used but a custom `backoff` can be

provided.



There are three built-in backoff strategies but a custom backoff strategy can be

written by implementing the `Backoff` interface.



**ConstantBackoff**



This backoff strategy will make the `WebSocket` client wait a constant amount of

time between reconnection attempts.



```dart

// Wait a constant 1s between reconnection attempts.

// [1, 1, 1, ...]

const backoff = ConstantBackoff(Duration(seconds: 1));

final socket = WebSocket(uri, backoff: backoff);

```



**LinearBackoff**



This backoff strategy will make the `WebSocket` client wait a linearly

increasing amount of time until an optional maximum duration is reached.



```dart

// Initially wait 0s and increase the wait time by 1s until a maximum of 5s is reached.

// [0, 1, 2, 3, 4, 5, 5, 5, ...]

const backoff = LinearBackoff(

  initial: Duration(seconds: 0),

  increment: Duration(seconds: 1),

  maximum: Duration(seconds: 5),

);

final socket = WebSocket(uri, backoff: backoff);

```



**BinaryExponentialBackoff**



This backoff strategy will make the `WebSocket` client wait an exponentially

increasing amount of time until a maximum step is reached.



```dart

// Initially wait 1s and double the wait time until a maximum step of of 3 is reached.

// [1, 2, 4, 4, 4, ...]

const backoff = BinaryExponentialBackoff(

  initial: Duration(seconds: 1),

  maximumStep: 3

);

final socket = WebSocket(uri, backoff: backoff);

```



## Monitoring the Connection ⚡️



The `WebSocket` client exposes a `connection` object which can be used to query

the connection state at any given time as well as listen to real-time changes in

the connection state.



```dart

final uri = Uri.parse('ws://localhost:8080');

final socket = WebSocket(uri);



// Listen to changes in the connection state.

socket.connection.listen((state) {

  // Handle changes in the connection state.

});



// Query the current connection state.

final connectionState = socket.connection.state;

```



The connection state can be one of the following:



- **connecting**: the connection has not yet been established.

- **connected**: the connection is established and communication is possible.

- **reconnecting**: the connection was lost and is in the process of being

  re-established.

- **reconnected**: the connection was lost and has been re-established.

- **disconnecting**: the connection is going through the closing handshake or

  the `close` method has been invoked.

- **disconnected**: the WebSocket connection has been closed or could not be

  established.



_\* The disconnected connection state contains nullable fields for the close

code, close reason, error, and stack trace._



## Sending Messages 📤



Once a `WebSocket` connection has been established, messages can be sent to the

server via `send`:



```dart

final socket = WebSocket(Uri.parse('ws://localhost:8080'));



// Wait until a connection has been established.

await socket.connection.firstWhere((state) => state is Connected);



// Send a message to the server.

socket.send('ping');

```



## Receiving Messages 📥



Listen for incoming messages from the server via the `messages` stream:



```dart

final socket = WebSocket(Uri.parse('ws://localhost:8080'));



// Listen for incoming messages.

socket.messages.listen((message) {

  // Handle the incoming message.

});

```



## Protobuf 💬



If you're using `web_socket_client` on the web with Protobuf, you might

want to use `binaryType` when initializing the `WebSocket` class.

`binaryType` is only applicable on the web and is not used on desktop or mobile platforms.



```dart

final socket = WebSocket(Uri.parse('ws://localhost:8080'), binaryType: 'arraybuffer');

```



See https://developer.mozilla.org/en-US/docs/Web/API/WebSocket/binaryType for more info.



## Closing the Connection 🚫



Once a `WebSocket` connection is established, it will automatically attempt to

reconnect if the connection is disrupted. Calling `close()` will update the

connection state to `disconnecting`, perform the closing handshake, and set the

state to `disconnected`. At this point, the `WebSocket` client will not attempt

to reconnect and a new `WebSocket` client instance will need to be created in

order to establish a new connection.



```dart

final socket = WebSocket(Uri.parse('ws://localhost:8080'));



// Later, close the connection with an optional code and reason.

socket.close(1000, 'CLOSE_NORMAL');

```



[build_badge]: https://github.com/felangel/web_socket_client/actions/workflows/main.yaml/badge.svg

[build_link]: https://github.com/felangel/web_socket_client/actions/workflows/main.yaml

[coverage_badge]: https://raw.githubusercontent.com/felangel/web_socket_client/main/coverage_badge.svg

[license_badge]: https://img.shields.io/badge/license-MIT-blue.svg

[license_link]: https://opensource.org/licenses/MIT

[pub_badge]: https://img.shields.io/pub/v/web_socket_client.svg

[pub_link]: https://pub.dartlang.org/packages/web_socket_client

[very_good_analysis_badge]: https://img.shields.io/badge/style-very_good_analysis-B22C89.svg

[very_good_analysis_link]: https://pub.dev/packages/very_good_analysis