Where is the error in WCF or WinForms?

Question

C++ / C#

Good afternoon!
I have been tormented for a day in search of a solution to the problem, an error occurs when working with WCF and WinForm.
When a response is received from WCF, a connection aborted message is thrown.
On the server, line 2 confirms that the data was processed without errors, but an error occurred when transferring to WinForm :(
Error:

Server:

Answer 1

https://www.linqpad.net/ to your WCF, and you will already remove 50% of the guesswork.
Practical guide. Stepping through WCF services