Whenever you use WinPcap, you are forced to select a specific network adapter to capture packets.
This sample shows you how to select the best network adapter automatically by using "GetBestInteface" win32 API.
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Thank you.

pcap_if_t* findBestAdapter(PIP_ADAPTER_INFO allIPAdaptersInfo, pcap_if_t* alldevs)

{

  DWORD  bestIfIndex;

  IPAddr ipAddr = htonl(0x08080808); // "8.8.8.8" is well-knowon Google DNS Server IP.

  DWORD res = GetBestInterface(ipAddr, &bestIfIndex);

  if (res != NO_ERROR)

  {

    printf("GetBestInterface return %d", res);

    return NULL;

  }

 

  PIP_ADAPTER_INFO p = allIPAdaptersInfo;

  while (p != NULL)

  {

    if (bestIfIndex == p->Index) break;

    p = p->Next;

  }

  if (p == NULL)

  {

    printf("Can not find appropriate system adapter\n");

    return NULL;

  }

 

  pcap_if_t *d = alldevs;

  while (d != NULL)

  {

    if (strstr(d->name, p->AdapterName) != NULL)

      break;

  }

  if (d == NULL)

  {

    printf("Can not find appropriate winpcap adapter\n");

    return NULL;

  }

  return d;

}



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