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1012

answers:

3

Hi,

I have a client-server system, both sides written by me, and I would like to put the clients in an 'offline' state when the server disconnects/dies, and then automatically bring them back 'online' when the server is available again.

For the first part, I listen for channel faulted events and handle that by setting the client to offline. I then start calling a 'ping' service on the server (every 30 sec.) which just returns a bool if it is alive. Once it is alive the client gets the bool and switches back online.

This all works, the problem I am having is that when the client calls the ping service and the server is down, no response is sent (obviously) and eventually, after about 2mins I get an endpoint not found exception. By this time I have already tried 3-4 more pings and hence have 3-4 exceptions brewing.

My question is, how can I deal with the ping service more gracefully? Ideally I would like to periodically call a service that lets me know if it is online, and instantly lets me know if it is not.

Thanks, Will

A: 

Does this help: CodeProject

Scott Whitlock
+4  A: 

What about this:

  • if you detect a server disconnect, enter a "Ping" mode
  • in the "ping mode", you set the client's "sendTimeout" to something very short, e.g. something like 2 secs or so, since your call to the service's Ping method should be answered almost immediately
  • once your "Ping" worked successfully, you again re-create the client proxy and set the client's "sendTimeout" back to the original value (default is 1 minute - depends on what makes sense for you, 15 seconds, 30 seconds - whatever)

That way, if you're in "Ping mode", you get your responses (or timeouts) quickly and you can detect the availability of the service quickly.

Marc

marc_s
Thanks Marc, great idea this is what I have done. I had completely forgotten that one can edit binding timeouts on the fly like this.
WillH
A: 

There's a related question here: http://stackoverflow.com/questions/881754/how-to-check-the-availability-of-a-net-tcp-wcf-service/883780#883780

There's a lot of options in that question.

Anderson Imes
Thanks Anderson, I searched as best I could before asking this question and thought I had spotted all the relevant posts but hadn't seen this one. Some very interesting reading, thanks.
WillH
Not a problem... it's actually a poorly worded subject... hard to find.
Anderson Imes