After a Windows Vista-based computer sends a POST request to a Web server, the same request is resent


After a Windows Vista-based computer uses a Windows HTTP Services (WinHTTP) component, such as the ServerXmlHttp object, to send a POST request to a Web server, the same request is resent to the server.

This behavior occurs if the keep-alive connection that is used for the first POST request is reset by the Web server.

Note To verify this behavior, you can use a network sniffer, or you can check the WinHTTP log.


WinHTTP does not distinguish between a direct connection and a connection that uses a proxy server. For more information, see the “8.2.4 Client Behavior if Server Prematurely Closes Connection” section of Request for Comments (RFC) 2616, “Hypertext Transfer Protocol — HTTP/1.1.” To do this, visit the following Internet Engineering Task Force (IETF) Web site: (

WinHTTP assumes that the server did not receive the POST request when it detects that the connection has been reset on the Web server. And then, WinHTTP resends the complete POST request.


This behavior is by design.


Unlike Internet Explorer, WinHTTP does not have a feature key mechanism for WinHTTP-related applications. Therefore, adding a registry entry to change this behavior in WinHTTP may cause unintended application compatibility issues on other WinHTTP-based clients.


Windows Vista Enterprise 64-bit Edition
Windows Vista Home Basic 64-bit Edition
Windows Vista Home Premium 64-bit Edition
Windows Vista Ultimate 64-bit Edition
Windows Vista Business
Windows Vista Business 64-bit Edition
Windows Vista Enterprise
Windows Vista Home Basic
Windows Vista Home Premium
Windows Vista Ultimate


Microsoft Knowledge Base Article

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