Edit:
Compability
XSockets will be websocket compatible on any machine running .NET 4,0 (or later) or Mono. This is regardless of operating system... You can even run the complete XSockets on a Raspberry PI if you want to. The only time XSockets will use the fallback is if the client connecting does not support websockets (IE9, IE8 etc).
SignalR has built the WebSocket support upon .NET 4.5 and the built-in WebSocket namespace (in 4.5) while XSockets has implemented the WebSocket protocol in .NET 4.0 (among other things). SignalR and XSockets has really nothing in comment besides that they both are built on .NET framework, after that the look very different... But that is out of scope.
Environment
Since XSockets has implemented the WebSocket protocol by it self this means that XSockets is not dependent on any webserver, IIS, Apache etc... It can run as a standalone windows service or on Azure if you like. However, you can also start XSockets within your web and that´s actually how it is setup when you install our nuget package.
Fallback
When you install XSockets into a MVC3/MVC4 solution the installation will automatically register an additional controller. This controller will use our External API (sockets) to communicate with XSockets and the JavaScript API will do AJAX (longpolling) against this controller if the client lacks support for websockets. As a developer you do not need to do anything different besides adding an additional JavaScript file if you want to use the fallback.
Now, you can make the fallback work for WebForms (and Azure) as well, but since that is out of scope we leave that for later if you have questions about it.
Bottom Line To wrap up...
- Do not worry about XSockets needing a special OS for running, we run on any Windows/Unix/Linux environment as long as .NET 4.0 or Mono is installed.
- XSockets run inside IIS, in Azure, as a Windows Service or just a console application... You can even run the server on Raspberry PI or anything else really (a phone or whatever) as long as the requirements for .NET/Mono is full filled.
- XSockets can be developed both in .NET/Mono environments, so you can actually develop plugin from both a MAC using Xamarin and Windows using Visual Studio.
- The fallback get automatically setup when you install it for development in MVC3/MVC4 but you can also setup fallback on Azure and WebForms.
- SignalR have the server environment deciding whether the clients can use websockets or not, XSockets always have websockets and fallback to longpolling only when the client does not support websockets.