🚀 go-pugleaf

Dear all,

I am thinking of developing a sniffer program to monitor packets on two
servers.  I referenced some samples on the web and found several
interesting.  One of which was developed in Delphi so changing it into BCB
would not be hard.

I did some porting and have a trial, and found it has a short-coming.  The
program uses raw socket to capture packets between two machines.  It does
the capture in a thread:

//--------------------------------------------------------------------------
-
void __fastcall TSnifferThread::Execute()
{
  //---- Place thread code here ----
  int         addr, iRet;

  iMySocketState = InitSocket(); /* Initialize the SOCKET */

  while(!Terminated)
  {
    // Save the received packet into a buffer
    iRet = recv(RawSocket, buf, sizeof(buf), 0);

    if(iRet == -1)
      continue;

    pipheader = PIP_Header(buf); // Transform the received packet into a
defined structure

    if((pipheader->ip_destaddr != FDestIp) || (pipheader->ip_srcaddr !=
FSrcIp))
      continue;

    // Display the packet information on a main thread's ListView
    try
    {
      pBuf = new char[iRet];
      CopyMemory(pBuf, buf, iRet);
      Synchronize(AddListItem);
    }
    __finally
    {
      if(pBuf != (char *)NULL)
      {
        delete pBuf;
        pBuf = (char *)NULL;
      }
    }

    Application->ProcessMessages();
  }

  if(ip != (char *)NULL)
  {
    delete ip;
    ip = (char *)NULL;
  }
}

The problem is, the thread keeps looping tightly to capture packets, causing
almost 100% CPU usage.  Are there other means to capture packets without a
tight loop, while packets would not be missed?

Many thanks,
Patrick