callback invalid in wcf service

I have a win forms client that accesses a wcf service for a long running operation. The service exposes subscribe and unsubscribe methods. When a client calls the subscribe method, service generates new guid for it and gets the current callback context, saves this guid and callback context in a client Dictionary and returns the Guid. On user request, client call service with this guid to start the long operation. Once the service finishes the operation it gives a callback to the client. the client then retrieves the processed data from the service.

The error I get sometimes when doing a callback is

The operation 'OnServiceCallback' could not be completed because the sessionful channel timed out waiting to receive a message. To i开发者_C百科ncrease the timeout, either set the receiveTimeout property on the binding in your configuration file, or set the ReceiveTimeout property on the Binding directly.

The part that I am not able to understand is that this happens very inconsistently. Most of the times it happens after the client and the service have been running for some time.

I am a beginner in wcf service and welcome any suggestions to solve this error.

Binding has property called receiveTimeout. This property is by default set to 10 minutes. It defines how long does the service instance wait for next request before it is terminated. So if there is no activity between client and service within 10 minutes your service instance is closed and client can't use it any more. In duplex service it can be even more complicated because there are services on both sides. You will probably need to configure receiveTimeout on both ends.

I was able to figure the answer to the error by doing some good old trial and error. The callback was failing because the OperationContext.Current object that I was trying to use was null. This was because I was trying to access the OperationContext.Current object on a thread which was different from the service thread. So to solve that I am now accessing the OperationContext.Current object in the service thread and then passing the callbackContext as a parameter to the external processing logic which actually needs to use it.