Article ID: 258425 - Last Review: February 28, 2007 - Revision: 3.3

Unable to specify HTTP version by using HttpOpenRequest()

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SYMPTOMS

When you make a WinInet API HttpOpenRequest call, the lpszVersion parameter is used to specify the requested HTTP version. Although it is possible to specify a specific HTTP version (such as HTTP/1.0), WinInet may ignore this parameter depending on the default HTTP protocol version set in the registry.

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CAUSE

If HTTP/1.1 is specified in the registry, WinInet overrides the lpszVersion parameter specified. By default, Internet Explorer 5.01 is set to use HTTP/1.1 for typical connections and HTTP/1.0 through a proxy. The registry keys that control this include the following keys.

For typical connections:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
"EnableHttp1_1"=dword:00000001 (default for HTTP/1.1 enabled)

For proxy connections:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
"ProxyHttp1.1"=dword:00000000 (default for HTTP/1.1 disabled through proxy)

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WORKAROUND

Disable HTTP/1.1 on all connections. You can do this by clicking to clear the Use HTTP 1.1 and Use HTTP 1.1 through proxy connections check boxes in the advanced properties of Internet Explorer. You can also do this programmatically by changing the registry keys listed earlier.

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