C# client for Server Side Events (EventSource)

Examples of one way streaming from server to client can be found on the web but it’s pretty much always JavaScript clients.  Here is a working example using the .NET stack, with WebAPI as the server and a C# console application as the client.

Download and run this WebAPI chat application which emits Server Side Events:

https://github.com/filipw/html5-push-asp.net-web-api/

I then open Visual Studio running as admin, update the code to use IIS with my machine name (Zeus) and a virtual directory, clicking the create virtual directory button, so I can track requests using Fiddler:

Then update the JavaScript within the app to use the same path:

The create a Console application, using NUGET add Json.NET and paste this code in:

using System;
using System.IO;
using System.Net;
using System.Text;
using Newtonsoft.Json;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            new WebClientWrapper();
            Console.ReadKey();
        }
    }

    public class WebClientWrapper
    {
        WebClient wc { get; set; }

        public WebClientWrapper()
        {
            InitialiseWebClient();   
        }

        // When SSE (Server side event) occurs this fires
        private void OnOpenReadCompleted(object sender, OpenReadCompletedEventArgs args)
        {
            using (var streamReader = new StreamReader(args.Result, Encoding.UTF8))
            {
                var cometPayload = streamReader.ReadLine();
                var jsonPayload = cometPayload.Substring(5);
                var message = JsonConvert.DeserializeObject<Message>(jsonPayload);
                Console.WriteLine("Message received: {0} {1} {2}", message.dt, message.username, message.text);
                InitialiseWebClient();
            }
        }

        private void InitialiseWebClient()
        {
            wc = new WebClient();
            wc.OpenReadAsync(new Uri("http://zeus/chatapp/api/chat/"));
            wc.OpenReadCompleted += OnOpenReadCompleted;
        }
    }

    public class Message
    {
        public string username { get; set; }
        public string text { get; set; }
        public string dt { get; set; }
    }
}

You’ll need to update the code for your machine name.

Now run Fiddler, the WebAPI project and the console app and add a message in the chat window:

In Fiddler, select the request your console just made and select Raw, you’ll see nothing.  Now right click and select COMETPeek and you’ll see the payload that was streamed.