Problem with WCF client calling one-way operation

I would take a look at this article as well by Gerben van Loon here. One way operation might not really be one way according to the standards.

It looks like SAP PI incorrectly sends an empty SOAP envelope and .NET incorrectly interprets that envelope.

Some options from this thread:

• alter the generated proxy and remove OneWay=true (or add OneWay=false) to the method definition
• catch the Protocol Violation in an exception handler and ignore it
• use a 2.0 style webreference to call the service
• apply SAP patch Note 1459995 - Soap Sender Adapter HTTP 202 and add &responsecode202=true to the url

The first and last options both worked for me. Further discussion on this sap.com thread.