.Net 2.0: How to subscribe to a event publisher on a remote computer using transient subscriptions?

Question

My problem is that I want to have a server application (on a remote computer) to publish certain events to several client computers. The server and client communicate using .Net-Remoting so currently I am using remoted .Net-Events to get the functionality. But there is one drawback: when the server (the event publisher) comes offline and is restarted, the clients lose the connection since the remote object references become invalid.

I am looking into Loosely Coupled Events and Transient COM Subscriptions to solve this issue. I put together a small demo application with one publisher and two subscribers. It works beautifully on one computer.

I am using the COMAdmin-Libraries to create a transient subscription for the event subscribers. The code looks like this:

MyEventHandler handler = new MyEventHandler();
ICOMAdminCatalog catalog;
ICatalogCollection transientCollection;
ICatalogObject subscription;
catalog = (ICOMAdminCatalog)new COMAdminCatalog();
transientCollection = (ICatalogCollection)catalog.GetCollection("TransientSubscriptions");
subscription = (ICatalogObject)transientCollection.Add();
subscription.set_Value("Name", "SubTrans");
subscription.set_Value("SubscriberInterface", handler);
string eventClassString = "{B57E128F-DB28-451b-99D3-0F81DA487EDE}";
subscription.set_Value("EventCLSID", eventClassString);
string sinkString = "{9A616A06-4F8D-4fbc-B47F-482C24A04F35}";
subscription.set_Value("InterfaceID", sinkString);
subscription.set_Value("FilterCriteria", "");
subscription.set_Value("PublisherID", "");
transientCollection.SaveChanges();
handler.Event1 += OnEvent1;
handler.Event2 += OnEvent2;

My question now is: what do I have to change in the subscription to make this work over a network? Is it even possible?

Answer 1

If your server comes offline every once and a while I cannot see how you can avoid to poll it to check that it is alive.

Answer 2

What about MSMQ? It seems perfect for what you are trying to achieve? You can use a traditional publish/subscribe model or multicast the messages.

Answer 3

This might be a step too far, but have you considered using WCF and the callback element of WCF?

Callback effectively turns the what was client into a server. To be honest, I don't know a great deal about callback and have only experimented. Perhaps worth a 10 minute google though.

Answer 4

As you are talking about COM and remote computers, I suspect you'll have to do some DCOM security configuration.