I am just always getting a bit nervous passing pure strings around. Particularly when you need to find references across the source code...Not sure if implementing a solution as outlined in Effective Java 2nd Edition, page 165 (Item 34 - Emulate extensible enums with interfaces) is worthwhile.

However, do you think it might add value to add at least a thin wrapper around the Strings? (E.g. call it TcpConnectionEventType)