Just to clarify since the naming might be a little confusing - NetCoreStack is Gencebay's project. Looks very cool, I'll mention it on our next ASP.NET Community Standup (http://live.asp.net). The ASP.NET team recently released a WebSocket implementation (https://github.com/aspnet/WebSockets) but it's not very full featured yet. For instance, the NetCoreStack project has some proxy handling, whereas I don't think the ASP.NET team's implementation handles proxies yet.

SignalR for .NET Core is under active development (https://github.com/aspnet/signalr), but a release date hasn't been announced. SignalR brings in things like connection and group management, and the update can take advantage of some of the performance and architectural changes in .NET Core.

[Disclaimer: Microsoft employee, Nazgûl]