Can you enlighten me on how to create a C# WCF client to consume OSB asynchronous web service? The protocol is https, soap11 with ws-addressing, and the replyto address for the callback has to be specified not anonymous. I could not find any wcf bindings including custom binding to work with OSB async web service so I created a wcf client that just sends the request while I have a separate wcf service to handle the callback response from the OSB. The wcf client works fine but my wcf service could not process the callback response. Using Wireshark to monitor the activities, I see the caallback respionse came in but encounter an error: HTTP/1.1 500 Internal Server Error..Content-Length: 751..Content-Type: text/xml; charset=utf-8..Server: Microsoft-HTTPAPI/2.0. So what's the right way to write WCF web service client to consume async OSB web service? Any help would be greatly appreciated.