How to detect a disconnection as soon as it happens on ASP.NET without polling?

Question

I have a server-sent events handler in ASP.NET

Response.ContentType = "text/event-stream";
while (true)
{
   if(thereIsAMessage)
   {
       Response.Write(message);
       Response.Flush();
       if (Response.IsClientConnected == false)
       {
           break;
       }
   }

   System.Threading.Thread.Sleep(1000);
}

The problem is that I can only detect a client disconnection when I send something to the client. And I don't want to poll it, which defeats the whole purpose of using Server-sent events in the first place.

Answer 1

Try to look at SignalR - useful for long polling, server notifications won't be difficult to implement. Uses websockets when available. Yours scenario can be implemented very easily using hubs.

Answer 2

If you want to do in your own code, you can simply modify your example:

Response.ContentType = "text/event-stream";
while (Response.IsClientConnected)
{
   if(thereIsAMessage)
   {
       Response.Write(message);
       Response.Flush();
   }

   System.Threading.Thread.Sleep(1000);
}

But still, I'm not sure this is optimal implementation using Thread.Sleep approach.