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;

Thats it... now dont forget to leave me Feedbacks :)

Regions and Clipping Window to Custom Shapes (Win32 VC++)

Intro.

You might have noticed certain applications have window which differ from the standard, normal window with Rectangle shape, a Title bar, Size bar and System menu. Well, a most common example is the Windows Media Player which can be found on Windows XP versions. The Windows Media Player 9 series Installed by default on all Microsoft WindowsXP OS possesses a different appearence on screen, with a new window shape and appearence. You should also thought about how to make your application's window also customized and re-shaped like that. Well, thats a good idea when thinking about GUI and dressing up your application's window.

How to do.

Before getting into the code, lets learn about something about Window Regions. Well, when talking about regions some people may wonder what this "region" is. The "Region" we use here in a window is exactly whatthe name denotes. It can be a specific area of any defined shape. There is nothing strict that a region must be rectangle. A region can be sphere, elliptic or any other combined shape you desire.To apply a region to a window, you must first declare a region handle (HRGN), define the region with calls to CreateRectRgn, CreateEllipticRgn, or CreatePolygonRgn( Refer to MSDN for more Region API's ). Then combine your regions( only if you have multiple regions defined) into one region with calls to CombineRgn, and then apply the final region to your window with a call to SetWindowRgn.

A region is an object, so you should DeleteObject them when you are done with them. :-)

I'm going to demonstrate a sample window with two Regions. Both are elliptical regions and i combine both these regions to a single one. Finally, i clip or cut my window in shape of this new custom region. The WIndow shape is modified to a defined region by using SetWindowRgn() API.

Code.

HRGN hRegion1 = CreateEllipticRgn(0, 30 , 200, 200);

HRGN hRegion2 = CreateEllipticRgn(0, 180, 200, 200);

CombineRgn(hRegion1, hRegion1, hRegion2, RGN_OR);

SetWindowRgn(hWnd, hRegion1, true);

DeleteObject(hRegion1);

DeleteObject(hRegion2);

The RGN_OR flag set in CombineRgn() performs logical ORing operation with both the regions, and apply it to the Window using a call to SetWindowRgn().

Now, you have a strange window shape. Since there is no Title Bar and Standard Window Buttons, you cannot drag the Window over the screen or you cannot close or minimize it. So, you have to close the application from Debugger or from Task Manager in Windows. You can add custom buttons by your own for Close and Minimize operation or whatever you like in this window. Now, what's the deal with Dragging?

A window which cannot be dragged across the screen is unimaginable and will be weird. The Window's title bar which helps us to drag is clipped away. Dont worry, we have a solution say a trick.

We will trick the Window whenever a left mouseclick happens within the window region to convince it the click happened on its Title bar. So, when we click inside the window and drag, it will get dragged across the screen as if it were dragged by clicking its titlebar.

We'll need to add the following case to our message handler's switch:

case WM_LBUTTONDOWN:

SendMessage( hWnd, WM_NCLBUTTONDOWN, HTCAPTION, NULL );

break;

WM_LBUTTONDOWN is sent whenever the user presses the left mouse button while the mouse is over the window. So when we catch this message, we send a WM_NCLBUTTONDOWN message to the title bar (HTCAPTION), tricking it into thinking we clicked it. Remember, clipping window will not delete other parts of the window. So, the titlebar is still present but not visible and it still has a message handler waiting for processing messages.

PS : Feedbacks helps me to know and improve :=)

How to get a session state change notification in Windows-(Win32)

Intro.

Every Windows users must be familiar with the term session. Generally, a session in windows is the time between Windows is booted to the time of Shutdown. The session has some states which can get changed dynamically while Windows runs. These state changes include User Logoff, User Logons, Lockdown and Unlock of users, Remote logon and logoff etc. We have nothing to do with these session states, but there are certain situations in which we may need to catchup these session state change and prepare our application to do certain tasks accordingly.

How to do.

The Windows Terminal Service helps us to recognize and get notified about session state change windows messages. The session state message is sent only to applications that have registered to receive this message by calling WTS API WTSRegisterSessionNotification(). After registered, the application starts to get notified of session state change windows messages. We can process these messages to get session events such as User Logon, Logoff, Lockdown and Unlock etc.

Code.

First of all, add this line of code in the WM_CREATE message handling section of your Application Window. If your application does not have a Window, add this in your main().

WTSRegisterSessionNotification( hWnd, NOTIFY_FOR_ALL_SESSIONS ) ;

Now our program begins getting WM_WTSSESSION_CHANGE message from Windows Terminal Service whenever a session event occurs. Next step is very simple. We just need to catch up the session state messages from wParam of this message, and handle them acordingly.

Add this block of code in your Message Handler. :-

case WM_WTSSESSION_CHANGE:

  wmSessionStat = LOWORD(wParam);

  switch( wmSessionStat )

   {

     case WTS_SESSION_LOCK:

     //The session is getting locked.

     break;

     case WTS_SESSION_UNLOCK:

     //A session is unlocked.

     break;

     case WTS_SESSION_LOGON:

     //A User logged in.

     break;

     case WTS_SESSION_LOGOFF:

     //A user is logging out.

     break;

     case WTS_REMOTE_CONNECT:

     //A session connected remotely.

     break;

     case WTS_REMOTE_DISCONNECT:

     //A session is getting disconnected remotely.

     break;

   }

break;

I hope i explained well. Rest is the work of MSDN and You. 8-)

Comments and Feedbacks expected :-)