WCF Client/Server application send request via proxy server instead of directing to server

Question

I am developing a client server application using Windows Communication Foundation.

There is an issue that although we set server ip address as exception list of proxy configuration but request (via HTTP/XML) from a client for service execution is still sent via the proxy server instead of directing to the server.

※ It is not all the requests. The rate is about 10%-20%. I would like to hear about the cause and advice for this issue.

The following is information that we found in the current issue.

• The rate of occurrence is high when WCF is used for the first time after the client is started.
• The IP address of the server is set in exception list (not use proxy) of proxy configuration
• Although the HTTP request is send via Proxy server, it header still set to Server IP.
• Even when sent to the proxy, the IP address of the server is set in the HTTP header of the request.
• There is no other application using WCF on the client.

[Environmental information]

1. Client

   OS Version: Windows 7 embedded

   Client proxy settings [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings](When the client shutdown, proxy information is updated)

   Proxy: Proxy IP Address: Port Number (ppp.ppp.ppp.ppp: 8080)

   Proxy exception list: IP address of server (sss.sss.sss.sss) WCF settings Address: http: //sss.sss.sss.sss/xxxx/yyyy.svc Binding: BasicHTTPBinding

2. Server

   OS Version: Windows Server 2016

   IIS Version: Microsoft-IIS / 10.0

   ASP.NET Version: 4.0.30319