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c#server-sent-events

Implement sending Server Sent Events in C# (no ASP.NET / MVC / ...)

For a project, I need to implement SSE (Server Sent Events) in a C# Application. Although this may sound easy, I've got no clue how to solve this.

As I'm new to C# (though, not new to programming in general) I took an excursion to Google and tried to look for some sample code. From what I've seen so far, I could learn to build a HTTP Server with C# or consume server sent events. But I found nothing about sending SSEs.

What I'm trying to get my head around: how can I keep sending updated data over the incoming request? Normally, you get a request, do your thing and reply. Done, connection closed. But in this case I want to kind of "stick" to the response-stream and send new data through, each time an event in my application fires.

The problem, for me, lies in this event-based approach: it's not some intervall-based polling and updating. It's rather that the app goes like "Hey, something happend. I really should tell you about it!"

TL;DR: how can I hold on to that response-stream and send updates - not based on loops or timers, but each time certain events fire?

Also, before I forget: I know, there are libraries out there doing just that. But from what I've seen so far (and from what I've understood; correct me if I'm wrong) those solutions depend on ASP.NET / MVC / you name it. And as I'm just writing a "plain" C# application, I don't think I meet these requirements.

Solution

  • This sounds like a good fit for SignalR. Note SignalR is part of the ASP.NET family, however this does NOT require the ASP.NET framework (System.Web), or IIS, as mentioned in comments.

    To clarify, SignalR is part of ASP.NET. According to their site:

    ASP.NET is an open source web framework for building modern web apps and services with .NET. ASP.NET creates websites based on HTML5, CSS, and JavaScript that are simple, fast, and can scale to millions of users.

    SignalR has no hard dependency on System.Web or on IIS.

    You can self-host your ASP.Net application (see https://learn.microsoft.com/en-us/aspnet/signalr/overview/deployment/tutorial-signalr-self-host). If you use .net core, it is actually self-hosted by default and runs as a normal console application.