Flutter websocket disconnect listening

Question

In Flutter, I wanna listen to websocket disconnect event, how to achieve that? The websocket connect will be drop when app goes to background, I still not found a method to let it continuesly running in background (does anyone have solution?), So I have to detect if a websocket connect is lost or something, so that I can re-connect when lost connection. Pls help if anyone knows how to achieve that.

Answer 1

You can find out if websocket is closed by implementing onDone callback. See the example below:

      _channel = IOWebSocketChannel.connect(
        'ws://yourserver.com:port',
      );

      ///
      /// Start listening to new notifications / messages
      ///
      _channel.stream.listen(
        (dynamic message) {
          debugPrint('message $message');
        },
        onDone: () {
          debugPrint('ws channel closed');
        },
        onError: (error) {
          debugPrint('ws error $error');
        },
      );

Hope that helps.

Answer 2

Other answers around SO and the web suggest that you can't just keep sockets open in the background (which seems reasonable, you'd be keeping open network connections that may affect battery life). Depending on your use case, you might be better looking at Push Notifications or something that checks on a schedule.

• How to keep iphone ios xmpp connection alive while in the background?
• Websocket paused when android app goes to background
• https://www.quora.com/How-do-I-keep-Socket-IO-running-in-the-background-on-iOS

Answer 3

If your server closes the connection just use pinginterval like this

ws.pingInterval = const Duration(seconds: 5);

onDone should be called.

basic ping pong is enough.