WebSocket Channel: A Comprehensive Guide

WebSocket Channel provides cross-platform StreamChannel wrappers for WebSocket connections, enabling seamless communication between web applications and servers.

How to Use WebSocket Channel

To establish a WebSocket connection, use the WebSocketChannel class:

import 'package:web_socket_channel/web_socket_channel.dart';

final wsUrl = Uri.parse('ws://example.com');
final channel = WebSocketChannel.connect(wsUrl);

Once connected, you can listen for incoming messages and send messages to the server:

channel.stream.listen((message) {
  print('Received: $message');
});

channel.sink.add('Hello, server!');

Cross-Platform Implementation

WebSocket Channel includes platform-specific implementations that can be used for both WebSocket communication and server-side support:

• IOWebSocketChannel for Dart:io (server-side)
• HtmlWebSocketChannel for Dart:html (web client)

Key Features

In addition to the standard StreamChannel interface, WebSocket Channel offers several key features:

• Negotiated Protocol: The protocol getter provides information about the protocol negotiated for the socket.
• Close Information: The closeCode and closeReason getters indicate why the socket was closed.
• Customizable Closure: The WebSocketSink allows you to specify close codes and reasons when closing the connection.
• Handshake Support: The WebSocketChannel.signKey() method simplifies handshake implementation.

Protocol Status Codes

WebSocket Channel also provides constants for predefined WebSocket protocol status codes in the status library:

import 'package:web_socket_channel/status.dart' as status;

// Close the connection with a going away status
channel.sink.close(status.goingAway);

Conclusion

WebSocket Channel provides a comprehensive and cross-platform solution for WebSocket communication, offering both a flexible API and platform-specific implementations. Its rich feature set and support for protocol status codes make it an invaluable tool for building real-time applications.