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InternetSetStatusCallback function

The InternetSetStatusCallback function sets up a callback function that WinINet functions can call as progress is made during an operation.

Syntax


INTERNET_STATUS_CALLBACK InternetSetStatusCallback(
  _In_  HINTERNET hInternet,
  _In_  INTERNET_STATUS_CALLBACK lpfnInternetCallback
);

Parameters

hInternet [in]

The handle for which the callback is set.

lpfnInternetCallback [in]

A pointer to the callback function to call when progress is made, or NULL to remove the existing callback function. For more information about the callback function, see InternetStatusCallback.

Return value

Returns the previously defined status callback function if successful, NULL if there was no previously defined status callback function, or INTERNET_INVALID_STATUS_CALLBACK if the callback function is not valid.

Remarks

Both synchronous and asynchronous functions use the callback function to indicate the progress of the request, such as resolving a name, connecting to a server, and so on. The callback function is required for an asynchronous operation. The asynchronous request will call back to the application with INTERNET_STATUS_REQUEST_COMPLETE to indicate the request has been completed.

A callback function can be set on any handle, and is inherited by derived handles. A callback function can be changed using InternetSetStatusCallback, providing there are no pending requests that need to use the previous callback value. Note, however, that changing the callback function on a handle does not change the callbacks on derived handles, such as that returned by InternetConnect. You must change the callback function at each level.

Many of the WinINet functions perform several operations on the network. Each operation can take time to complete, and each can fail.

It is sometimes desirable to display status information during a long-term operation. You can display status information by setting up an Internet status callback function that cannot be removed as long as any callbacks or any asynchronous functions are pending.

After initiating InternetSetStatusCallback, the callback function can be accessed from within any WinINet function for monitoring time-intensive network operations.

Note  The callback function specified in the lpfnInternetCallback parameter will not be called on asynchronous operations for the request handle when the dwContext parameter of HttpOpenRequest is set to zero (INTERNET_NO_CALLBACK), or the connection handle when the dwContext handle of InternetConnect is set to zero (INTERNET_NO_CALLBACK).

Like all other aspects of the WinINet API, this function cannot be safely called from within DllMain or the constructors and destructors of global objects.

Note  WinINet does not support server implementations. In addition, it should not be used from a service. For server implementations or services use Microsoft Windows HTTP Services (WinHTTP).

Requirements

Minimum supported client

Windows 2000 Professional

Minimum supported server

Windows 2000 Server

Header

Wininet.h

Library

Wininet.lib

DLL

Wininet.dll

See also

Common Functions
WinINet Functions
InternetStatusCallback

 

 

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