Register for NLM events (INetworkListManager, Advise, Sink, etc.)

delphi, nlm, winapi

Solution

You are passing the wrong object to `Advise()`. You are passing the `IConnectionPointContainer` object. You need to instead write your own class that implements the `INetworkEvents` interface, then create an instance of the class and pass that object to `Advise()`. That is how the NLM (or any other COM object that uses Connection Points) is able to send events to your code.

Update: You need to change your `NLMEvents` unit to keep the NLM object alive after `StartNLMEventListener()` exits, then the events will work correctly. The way you have it coded, the NLM object is local to `StartNLMEventListener()` and thus is released when `StartNLMEventListener()` exits, which unregisters your event sink.

Try this instead:

unit NLMEvents;

interface

function StartNLMEventListener: HResult;
function StopNLMEventListener: HResult;

implementation

uses
  Windows, ActiveX, NETWORKLIST_TLB, SysUtils, Unit1;

type
  TMyNetworkEvents = class(TInterfacedObject, INetworkEvents, INetworkConnectionEvents, INetworkListManagerEvents)
  public
    function NetworkAdded(networkId: TGUID): HResult; stdcall;
    function NetworkConnectivityChanged(networkId: TGUID; NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
    function NetworkDeleted(networkId: TGUID): HResult; stdcall;
    function NetworkPropertyChanged(networkId: TGUID; fFlags: NLM_NETWORK_PROPERTY_CHANGE): HResult; stdcall;
    function ConnectivityChanged(NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
    function NetworkConnectionConnectivityChanged(networkId: TGUID; NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
    function NetworkConnectionPropertyChanged(networkId: TGUID; fFlags: NLM_NETWORK_PROPERTY_CHANGE): HResult; stdcall;
  end;

var
  pNLM: INetworkListManager = nil;
  dwCookie1: LongInt = -1;
  dwCookie2: LongInt = -1;
  dwCookie3: LongInt = -1;

const
  IID_IConnectionPointContainer: TGUID = '{B196B284-BAB4-101A-B69C-00AA00341D07}';
  //IID_IUnknown: TGUID = '{00000000-0000-0000-C000-000000000046}';
  //CLSID_NetworkListManager: TGUID = '{DCB00C01-570F-4A9B-8D69-199FDBA5723B}';

function TMyNetworkEvents.ConnectivityChanged(NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('ConnectivityChanged');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkConnectionConnectivityChanged(networkId: TGUID; NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkConnectionConnectivityChanged');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkConnectionPropertyChanged(networkId: TGUID; fFlags: NLM_NETWORK_PROPERTY_CHANGE): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkConnectionPropertyChange');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkAdded(networkId: TGUID): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkAdded');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkConnectivityChanged(networkId: TGUID; NewConnectivity: NLM_CONNECTIVITY): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkConnectivityChanged');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkDeleted(networkId: TGUID): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkDeleted');
  Result := S_OK;
end;

function TMyNetworkEvents.NetworkPropertyChanged(networkId: TGUID; fFlags: NLM_NETWORK_PROPERTY_CHANGE): HResult; stdcall;
begin
  Form2.Memo1.Lines.Add('NetworkPropertyChanged');
  Result := S_OK;
end;

function StartNLMEventListener: HResult;
var
  pCpc: IConnectionPointContainer;
  pConnectionPoint: IConnectionPoint;
  pSink: INetworkEvents;
begin
  if pNLM = nil then
  begin
    Result := CoCreateInstance(CLASS_NetworkListManager, nil, CLSCTX_ALL, IID_INetworkListManager, pNLM);
    if Failed(Result) then
      Exit;
  end else
  begin
    Result := S_OK;
  end;

  if Succeeded(pNLM.QueryInterface(IID_IConnectionPointContainer, pCpc)) then
  begin
    pSink := TMyNetworkEvents.Create as INetworkEvents;

    if dwCookie1 = -1 then
    begin
      if Succeeded(pCpc.FindConnectionPoint(IID_INetworkEvents, pConnectionPoint)) then
      begin
        pConnectionPoint.Advise(pSink, dwCookie1);
        pConnectionPoint := nil;
      end;
    end;

    if dwCookie2 = -1 then
    begin
      if Succeeded(pCpc.FindConnectionPoint(IID_INetworkConnectionEvents, pConnectionPoint)) then
      begin
        pConnectionPoint.Advise(pSink, dwCookie2);
        pConnectionPoint := nil;
      end;
    end;

    if dwCookie3 = -1 then
    begin
      if Succeeded(pCpc.FindConnectionPoint(IID_INetworkListManagerEvents, pConnectionPoint)) then
      begin
        pConnectionPoint.Advise(pSink, dwCookie3);
        pConnectionPoint := nil;
      end;
    end;
  end;
end;

function StopNLMEventListener: HResult;
var
  pCpc: IConnectionPointContainer;
  pConnectionPoint: IConnectionPoint;
begin
  if pNLM <> nil then
  begin
    if Succeeded(pNLM.QueryInterface(IID_IConnectionPointContainer, pCpc)) then
    begin
      if dwCookie1 <> -1 then
      begin
        if Succeeded(pCpc.FindConnectionPoint(IID_INetworkEvents, pConnectionPoint)) then
        begin
          pConnectionPoint.Unadvise(dwCookie1);
          pConnectionPoint := nil;
        end;
      end;

      if dwCookie2 <> -1 then
      begin
        if Succeeded(pCpc.FindConnectionPoint(IID_INetworkConnectionEvents, pConnectionPoint)) then
        begin
          pConnectionPoint.Unadvise(dwCookie2);
          pConnectionPoint := nil;
        end;
      end;

      if dwCookie3 <> -1 then
      begin
        if Succeeded(pCpc.FindConnectionPoint(IID_INetworkListManagerEvents, pConnectionPoint)) then
        begin
          pConnectionPoint.Unadvise(dwCookie3);
          pConnectionPoint := nil;
        end;
      end;
    end;

    pNLM := nil;
  end;

  dwCookie1 := -1;
  dwCookie2 := -1;
  dwCookie3 := -1;

  Result := S_OK;
end;

end.

Problem

Original source