I'm not sure of your API can you verify that this will work (it compiles):

1) Generate events from the filter, and convert into `Item`s, inserted into `NegentropyStorageVector`. [BUT I copied your NegentropyStorageVector and implemented `NegentropyStorageBase` for &NegentropyStorageVector to not consume it].

2) Store in a global HashMap under the subscription ID.

3) Look it up again immediately to get a `&NegentropyStorageVector` and build a `Negentropy` on it.

4) `reconcile()` the incoming bytes to get the outgoing bytes.

5) Next NEG-MSG, just start at step (3)

Also I deployed this at wss://chorus.mikedilger.com:444 but I don't have any tools for testing it. If anybody could easily check if negentropy is working there, that would be great. Otherwise I'll have to write some tool.