Resolver must be specified. The default resolver (PNRP) is not available
PeerChannel is part of the [WCF] framework that enables development of managed Peer-to-Peer applications.
More details about Peer Name Resolution Protocol (PNRP) here.
If you're developing a P2P application using WCF, and you run into the following exception when trying to open the service host:
"System.InvalidOperationException: Resolver must be specified. The default resolver (PNRP) is not available."
Since PNRP service is not enabled by default on Pre-Vista platforms you need to follow the steps below to make sure PNRP is up and running:
1. Go to Start > Run. Type Appwiz.cpl. This opens the ControlPanel – Add Remove Software dialog box. Choose Add Remove Windows Components and then choose Networking > Details. Make sure Peer-to-Peer is checked. Click Install.
2. Then, open up a cmd prompt and type "net start pnrpsvc". This should start up the installed pnrp service for us.
3. Run your project now. This should solve the problem.