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InternetOpen

HINTERNET InternetOpen(
    IN LPCSTR lpszAgent,
    IN DWORD dwAccessType,
    IN LPCSTR lpszProxyName,
    IN LPCSTR lpszProxyBypass,
    IN DWORD dwFlags
);

Initializes an application's use of the Win32 Internet functions.

• Returns a valid handle that the application passes on to subsequent Win32 Internet functions. If InternetOpen fails, it returns NULL. To get a specific error message, call GetLastError.

lpszAgent

Address of a string that contains the name of the application or entity calling the Internet functions (for example, Microsoft Internet Explorer). This name is used as the user agent in the HTTP protocol.

dwAccessType

Type of access required. Can be one of the following values:

INTERNET_OPEN_TYPE_DIRECT

Resolves all host names locally.

INTERNET_OPEN_TYPE_PRECONFIG

Retrieves the proxy or direct configuration from the registry.

INTERNET_OPEN_TYPE_PRECONFIG_WITH_NO_AUTOPROXY

Retrieves the proxy or direct configuration from the registry and prevents the use of a startup JScript or Internet Setup (INS) file.

INTERNET_OPEN_TYPE_PROXY

Passes requests to the proxy unless a proxy bypass list is supplied and the name to be resolved bypasses the proxy. In this case, the function uses INTERNET_OPEN_TYPE_DIRECT.

lpszProxyName

Address of a string that contains the name of the proxy server (or servers) to use if proxy access was specified. If this parameter is NULL, the function reads proxy information from the registry. Do not use an empty string, because InternetOpen will use it as the proxy name. The Win32 Internet functions only recognize CERN type proxies (HTTP only) and the TIS FTP gateway (FTP only). If Microsoft Internet Explorer is installed, the Win32 Internet functions also support SOCKS proxies. FTP and Gopher requests can be made through a CERN type proxy either by changing them to an HTTP request or by using InternetOpenUrl.

lpszProxyBypass

Address of an optional list of host names or IP addresses, or both, that should not be routed through the proxy. The list can contain wildcards. Do not use an empty string, because InternetOpen will use it as the proxy bypass list. If this parameter specifies the "<local>" macro as the only entry, the function bypasses any host name that does not contain a period. If this parameter is NULL, the function reads the bypass list from the registry.

dwFlags

Flags that indicate various options affecting the behavior of the function. Can be a combination of these values:

INTERNET_FLAG_ASYNC

INTERNET_FLAG_FROM_CACHE

INTERNET_FLAG_OFFLINE

InternetOpen is the first Win32 Internet function called by an application. It tells the Internet DLL to initialize internal data structures and prepare for future calls from the application. When the application finishes using the Internet functions, it should call InternetCloseHandle to free the handle and any associated resources.

The application can make any number of calls to InternetOpen, although a single call is normally sufficient. The application might need to have separate behaviors defined for each InternetOpen instance, such as different proxy servers configured for each.

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