SignalR 2.4.0 persistent connection, blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource

Question

User1497005810 posted

I have two projects. One is <g class="gr_ gr_11 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="11" data-gr-id="11"><g class="gr_ gr_15 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar only-ins replaceWithoutSep" id="15" data-gr-id="15">signalr</g></g> server. Another is webform(javascript) for <g class="gr_ gr_12 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="12" data-gr-id="12"><g class="gr_ gr_14 gr-alert gr_gramm gr_inline_cards gr_run_anim Grammar only-ins doubleReplace replaceWithoutSep" id="14" data-gr-id="14">signalr</g></g> client. Both are used .net framework 4.5 and <g class="gr_ gr_13 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="13" data-gr-id="13">signalr</g> 2.4.0 and persistent connection.

I have a problem. How do I add cors(<g class="gr_ gr_10 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="10" data-gr-id="10">cross domain</g>) in my <g class="gr_ gr_9 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="9" data-gr-id="9">signalr</g> server?

[assembly: OwinStartup(typeof(SignalRServer.Startup))]
namespace SignalRServer
{
	public class Startup
	{
		public void Configuration(IAppBuilder app)
		{			
			app.MapSignalR<EchoConnection>("/realtime/echo", new ConnectionConfiguration()
			{
				EnableJSONP = true
			});
		}
	}
}

Answer 1

User61956409 posted

Hi akira32,

I have two projects. One is signalr server. Another is webform(javascript) for signalr client. Both are used .net framework 4.5 and signalr 2.4.0 and persistent connection.

I have a problem. How do I add cors(cross domain) in my signalr server?

[This documentation](https://docs.microsoft.com/en-us/aspnet/signalr/overview/guide-to-the-api/hubs-api-guide-javascript-client#calling-usecors) demonstrates how to implement cross-domain connections in SignalR 2, please refer to it.

using Microsoft.AspNet.SignalR;
using Microsoft.Owin.Cors;
using Owin;
namespace MyWebApplication
{
    public class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            // Branch the pipeline here for requests that start with "/signalr"
            app.Map("/signalr", map =>
            {
                // Setup the CORS middleware to run before SignalR.
                // By default this will allow all origins. You can 
                // configure the set of origins and/or http verbs by
                // providing a cors options with a different policy.
                map.UseCors(CorsOptions.AllowAll);
                var hubConfiguration = new HubConfiguration 
                {
                    // You can enable JSONP by uncommenting line below.
                    // JSONP requests are insecure but some older browsers (and some
                    // versions of IE) require JSONP to work cross domain
                    // EnableJSONP = true
                };
                // Run the SignalR pipeline. We're not using MapSignalR
                // since this branch already runs under the "/signalr"
                // path.
                map.RunSignalR(hubConfiguration);
            });
        }
    }
}

With Regards,

Fei Han

Answer 2

User1497005810 posted

Thank you! I had solved my problem.

			app.Map("/realtime/echo", map =>
			{
				map.UseCors(CorsOptions.AllowAll);
				var ConnectionConfiguration = new ConnectionConfiguration
				{
					// You can enable JSONP by uncommenting line below.
					// JSONP requests are insecure but some older browsers (and some
					// versions of IE) require JSONP to work cross domain
					EnableJSONP = true
				};
				// Run the SignalR pipeline. We're not using MapSignalR
				// since this branch already runs under the "/signalr"
				// path.
				map.RunSignalR<EchoConnection>(ConnectionConfiguration);
			});