Non-global connection callbacks

[joshua-light]

Hi!

Is there a way to set a connection status handler callback for a specific NetworkingSockets instance?

Currently, it's recommended to use NetworkingUtils.SetStatusCallback. However, as far as I see, this sets a global per application callback, which doesn't allow to create both client and server in a single app.

Thanks!

[copyrat90]

Years late, but if you are still interested, you can take a look at copyrat90@f7f4e12

Although, I won't directly send a PR here, because I've added #23 and made some changes on the API.
(I've changed the API because there's more status callbacks other than connection status changed)