A proxy server is used as a security barrier between the internal network and the Internet. This helps to protect the internal network from unauthorized access. A proxy server also enhances speed performance because it caches recently used documents. To gain access to a proxy server, the Windows Mobile–based application needs a proxy authentication scheme.
When a Windows Mobile–based application tries to use a proxy server that requires authentication, the proxy returns a 407 status code message to the client. In that message, the proxy should include one or more Proxy-Authenticate response headers. These headers include the authentication methods available from the proxy. The Windows Internet Services (WinInet) functions select the first recognized method.
To obtain user name and password from the user the application can use the InternetErrorDlg function.
If no proxy user name and password are set, the WinInet functions attempt to use the user name and password for the server.