How to Disconnect/Release all Network Adapters using Win32 API (VC++)

Intro.

Here i am demonstrating on how to disconnect or how to close all network connections in a system by programming uing Win32 C++. There are hardly certain situations where we need to disconnect some, or all of the network connections and close the adapters. Anyway this can be done directly through a few API calls in Windows. Nothing is big deal about doing this task, and its quite easy.

How to do.

There is a Windows API function named GetInterfaceInfo() in the IP Helper functions library which allows us to enumerate all available Network Adapters installed in a system. Well, so we got all available adapters list filled by the above function. Next, our task is to release the adapter/adapters.. For that, we can use another IP helper API named IpReleaseAddress(). This function releases an IP address previously obtained through Dynamic Host Configuration Protocol (DHCP). We can set a loop, so all adapters can be Released.


Code.

Now here's the code outline...

#include "IpExport.h"

#include "Iphlpapi.h"

#pragma comment( lib, "iphlpapi" )

...

// Call GetInterfaceInfo() with empty buffer to get the required allocation size.

ULONG ulInfoLength = 0;

GetInterfaceInfo( 0, &ulInfoLength );

// Allocate buffer for PIP_INTERFACE_INFO

LPBYTE pInfoBuffer = new BYTE[ ulInfoLength ];

PIP_INTERFACE_INFO pInfo = ( PIP_INTERFACE_INFO )pInfoBuffer;

// Call GetInterfaceInfo() with valid buffer to get all Network Adapters

GetInterfaceInfo( pInfo, &ulInfoLength );

// Release all adapters one by one

for( LONG i = 0; iNumAdapters; ++i )

IpReleaseAddress( &pInfo->Adapter[ i ] );

// Delete the IP_INTERFACE_INFO buffer

delete []pInfoBuffer;

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