Socket does not throw error on unsuccessfull connection

test_socket_open.dart

#import("dart:io");
Future<Socket> openConnection(){  
  var socket = new Socket('127.0.0.1', 1234567);    
  Completer completer = new Completer();  
  socket.onError = (e) {
    print("connect exception ${e}");
    completer.completeException(e);
  };
  socket.onConnect = () {  
    completer.complete(socket);
  };
  
  return completer.future;    
}
void main() {
  openConnection().then((socket)=>print(socket));
}