Christopher Scrosati explains how tracing helps when debugging the server side PollingDuplex in Silverlight 4.
Did you know it is now easier to debug the server side PollingDuplex in Silverlight 4? With the addition of tracing, you can now get a peek at what is happening internally within your service. Traces from PollingDuplex will include information about what failed in communicating with your clients and how it was handled.