catch SocketException

Asynchronous errors can't be caught using try/catch(https://www.dartlang.org/docs/tutorials/futures/) at least unless you are using async/await(https://www.dartlang.org/articles/await-async/)

You can use the done future on the WebSocket object to get that error, e.g.:
import 'dart:async';
import 'dart:io';

main() async {
  // Connect to a web socket.
  WebSocket socket = await WebSocket.connect('ws://echo.websocket.org');

  // Setup listening.
  socket.listen((message) {
    print('message: $message');
  }, onError: (error) {
    print('error: $error');
  }, onDone: () {
    print('socket closed.');
  }, cancelOnError: true);

  // Add message, and then an error.
  socket.add('echo!');
  socket.addError(new Exception('error!'));

  // Wait for the socket to close.
  try {
    await socket.done;
    print('WebSocket donw');
  } catch (error) {
    print('WebScoket done with error $error');
  }
}
　　

I get your point, but I don't understand why this is an asynchronous error. I mean, you get this error before starting to actually asynchronously listen to requests, right? – Alexandr Sep 27 '15 at 16:41
1
HttpServer.bind() is already async (returns a Future<HttpServer>) – Günter Zöchbauer Sep 27 '15 at 16:43
You are right, Gunter. Thank you for this! – Alexandr Sep 28 '15 at 5:35