closeReason property
String closeReasonThe close reason set when the WebSocket connection is closed. If there is no close reason available this property will be null
Source
String get closeReason;
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-io/WebSocket/closeReason.html