SignalR - Sending a Message from a WCF Project

Question

I've followed the instructions from https://github.com/SignalR/SignalR/wiki/Hubs entitled "Broadcasting over a Hub from outside of a Hub".

I got this method working from within an MVC Action in the same project. Requesting the Action sends the update to connected clients.

My problem is that I need to be able to send updates from another project, in particular a WCF Web Services project. My app has an API and a web component and when API users make calls that change things, these updates need to be pushed out to the Web clients via SignalR. And calling a web service with the same code as my Test Action doesn't work.

I also tried the same code inside an nunit unit test that didn't work either.

What do I need to do to make this same method described on the Wiki work for a WCF Project?

Answer 1

I cannot get exactly what you aim. But if I understood correctly you're trying to send some kind of notifications raised inside WCF services to SignalR clients. If that's the case; I can suggest you my approach:

I have some WCF services and a SignalR hub in the same application server. IMHO, the best way to communicate WCF with SignalR hub is by using MSMQ. When a notification occurs inside a WCF service, it puts the notification payload into MSMQ. On the other end, SignalR hub listens the same queue. When a message put into the queue, it gets the content and broadcasts to the hub clients. Very easy and straightforward. No extra service/hub call at the server side.

SignalR hub can listen for new queue items by using System.Messaging.MessageQueue#ReceiveCompleted method. When this event raised, SignalR hub gets the queue item and broadcasts to its clients.

Answer 2

The easiest solution is probably to provide an API on your Web Application (use MVC or the new WebAPI) that broadcasts to all connected clients. Any other application (an NT Service, an NUnit test, ...) can call that API if it wants to send a message to the clients.

You can't expect SignalR to do anything if you aren't hosting a Hub either in a Web Application running under IIS, or another application hosting it directly.

If you need two-way communication from your separate application to your clients then simply make your application into a SignalR client too and have it communicate via the Web Application hosted SignalR to the clients and have it listen to messages from them too.

For example, here's how I have configured a complex Service + WebSite + Clients solution (ignore the purple for now):

The Live Web Server allows NT Services to connect and create SignalR Groups. NT Services send to those groups. Web browsers connect to a group and receive messages send to that group. In effect the middle box becomes a pubsubhub.