Occurs immediately after a packet has been received by the network adapter.

Syntax:

TOnPacketReceive = procedure (Sender : TObject;
                              ThParam: Pointer;
                              hPacket: Pointer;
                          pPacketData: Pointer;
                        IncPacketSize: DWORD) of object;

Parameters:

ThParam

[in] User defined thread parameter (see OnThreadBegin).

hPacket

[in] HNPacket object handle.

pPacketData

[in] A pointer to the packet data (see also PacketData).

IncPacketSize

[in] Packet size (see also IncPacketSize).

Description:

Packets processing code in the OnPacketReceive event handler must be as fast as possible because if the packets processing performance is low, and the network traffic is high, you run the risk of losing some packets.

Please use statistics to make sure that your application does not lose any packets.

For example, when you use a BPF filter, and if your application is in time to process all packets, then the value returned by Get_ProcessCount is equal to the Get_AcceptCount one.

If you do not use a filter, you should compare Get_ProcessCount and Get_RecvCount returned values. In this way you can check, whether your application is able to process the whole network traffic received by the Packet Sniffer SDK internal driver from the system.

When the network traffic is very high, it would be very appropriate to create a packets processing queue in your application, using a separate thread, and just enqueue the received packets in the OnPacketReceive event handler, and to notify this queue about the receiving of a new packet (see HNQueue).

Also, you should take into account that OnPacketReceive event handler is called in the context of a thread, created by Packet Sniffer SDK library.

We strongly recommend you to do nothing related to the data displaying in this event handler. If the traffic is high, such actions may lead to the hanging of the application and packets loss.

OnPacketReceive event handler example:

procedure TForm1.HNAdapterOnPacketReceive(Sender: TObject;
  ThParam, hPacket, pPacketData: Pointer; IncPacketSize: DWORD);
 var
  pEth:    PETHERNET_HEADER;
  EthType: Word;
  pArp:    PARP_HEADER;
begin
   HNPacket1.Handle := hPacket;
   if (HNPacket1.MediumType <> atEthernet) then Exit;

   pEth  := PETHERNET_HEADER(pPacketData);
   EthType := htons(pEth^.EthType);

   ...

   if(EthType = ETHERTYPE_ARP) then
    begin
      pArp := PARP_HEADER(@PByteArray(pPacketData)^[sizeof(ETHERNET_HEADER)]);
      MoveMemory(@DestMacAddr[0],@pArp^.Sndr_Hw_Addr[0],6);
      SetEvent(RecvArpPacket);
      Exit;
    end;

   ...
end;