Why SignalR does isn't use WebSockets?

Why SignalR does isn't use WebSockets?

As you probably know SignalR supports multiple transports. The favor one and most powerful one is of course WEBSOCKET transport.
Unfortunately this transport cannot is always used in any infrastructure. When your application is started the client side of SignalR would check what's transports is supported.
Interestingly there is a similar check at the server side.

For example, if you see following request

Post/daenet.myspy/signalr/signalr/send?transport=foreverframe&connectionid= cd17bb01-23de-4181-97da-6514b9bbb58e http/1.1

Which is responded by following response, it means the web socket transport is not supported. IF infrastructure does not the support streaming SIgnalR would use fallback transport. In a case of Internet Explorer this would be foreverframe as shown above.
To being sure that the server was not the problem, try-to-find out the request like following one:

Get/daenet.myspy/signalr/signalr/connect?transport=websockets&connectionid= Cd17bb01-23de-4181-97da-6514b9bbb58e&connectiondata=%5b%7b%22name%22%3a%22trackerhub%22%7d%5d&tid=6 http/1.1

If This request has a failed with error, it means that the server does is not a support websockets. Specific case server means the server (IIS) supports WebSockets, but ASP. Your application which hos TS SignalR does not the support websockets.
It sound Wired, buiit are not. If the server does not support WebSockets (for example Windows server), you'll never get error. The client would switch to fallback transport automatically. This error was related to ASP.
To fix it your need following in the Web. config:

<system.web>

<compilation debug= "true" targetframework= "4.5"/>

<pages controlrenderingcompatibilityversion= "4.0"/>
</system.web>

Http://localhost/MySpy/signalr/signalr/connect?transport=webSockets&connectionId= 829cc336-a32c-457a-b539-fca7744fda09&connectiondata=%5b%7b%22name%22%3a%22trackerhub%22%7d%5d&tid=7

Why SignalR does isn't use WebSockets?