SignalR客户端默认后备传输

Question

For the case of an SignalR client using .Net Framework 4.0 to connect to the server (therefore no WebSockets transport supported) which would be the next fallback transport ?

Moreover, if there is a fallback chain it would be great to know it.

Answer 1

From https://docs.microsoft.com/en-us/aspnet/signalr/overview/getting-started/introduction-to-signalr#transports-and-fallbacks the following are used if WebSockets is unavailable:

• Server Sent Events, also known as EventSource (if the browser supports Server Sent Events, which is basically all browsers except Internet Explorer.)
• Forever Frame (for Internet Explorer only). Forever Frame creates a hidden IFrame which makes a request to an endpoint on the server that does not complete. The server then continually sends script to the client which is immediately executed, providing a one-way realtime connection from server to client. The connection from client to server uses a separate connection from the server to client connection, and like a standard HTML request, a new connection is created for each piece of data that needs to be sent.
• Ajax long polling. Long polling does not create a persistent connection, but instead polls the server with a request that stays open until the server responds, at which point the connection closes, and a new connection is requested immediately. This may introduce some latency while the connection resets.

Update: The latest docs are available here: http://www.asp.net/signalr/overview/signalr-20/getting-started-with-signalr-20/introduction-to-signalr