FAddrResolved :   Boolean;
    procedure ResolveAddr;
  public
    constructor Create; virtual;
    destructor  Destroy; override;
    function    Ping : Integer;
    procedure   SetAddress(Value : String);
    function    GetErrorString : String;

    property Address       : String         read  FAddress   write SetAddress;
    property Size          : Integer        read  FSize      write FSize;
    property Timeout       : Integer        read  FTimeout   write FTimeout;
    property Reply         : TIcmpEchoReply read  FReply;
    property TTL           : Integer        read  FTTL       write FTTL;
    Property Flags         : Integer        read  FFlags     write FFlags;
    property ErrorCode     : DWORD          read  FLastError;
    property ErrorString   : String         read  GetErrorString;
    property HostName      : String         read  FHostName;
    property HostIP        : String         read  FHostIP;
    property OnDisplay     : TICMPDisplay   read  FOnDisplay write FOnDisplay;
    property OnEchoRequest : TNotifyEvent   read  FOnEchoRequest
                                            write FOnEchoRequest;
    property OnEchoReply   : TICMPReply     read  FOnEchoReply
                                            write FOnEchoReply;
  end;

  TICMPException = class(Exception);

implementation

{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
constructor TICMP.Create;
var
    WSAData: TWSAData;
begin
    hICMP    := INVALID_HANDLE_VALUE;
    FSize    := 56;
    FTTL     := 64;
    FTimeOut := 4000;

    // initialise winsock
    if WSAStartup($101, WSAData) <> 0 then
        raise TICMPException.Create('Error initialising Winsock');

    // register the icmp.dll stuff
    hICMPdll := LoadLibrary(icmpDLL);
    if hICMPdll = 0 then
        raise TICMPException.Create('Unable to register ' + icmpDLL);

    @ICMPCreateFile  := GetProcAddress(hICMPdll, 'IcmpCreateFile');
    @IcmpCloseHandle := GetProcAddress(hICMPdll, 'IcmpCloseHandle');
    @IcmpSendEcho    := GetProcAddress(hICMPdll, 'IcmpSendEcho');

    if (@ICMPCreateFile = Nil) or
       (@IcmpCloseHandle = Nil) or
       (@IcmpSendEcho = Nil) then
          raise TICMPException.Create('Error loading dll functions');

    hICMP := IcmpCreateFile;
    if hICMP = INVALID_HANDLE_VALUE then
        raise TICMPException.Create('Unable to get ping handle');
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
destructor TICMP.Destroy;
begin
    if hICMP <> INVALID_HANDLE_VALUE then
        IcmpCloseHandle(hICMP);
    if hICMPdll <> 0 then
        FreeLibrary(hICMPdll);
    WSACleanup;
    inherited Destroy;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
function MinInteger(X, Y: Integer): Integer;
begin
    if X >= Y then
        Result := Y
    else
        Result := X;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TICMP.ResolveAddr;
var
    Phe : PHostEnt;             // HostEntry buffer for name lookup
begin
    // Convert host address to IP address
    FIPAddress := inet_addr(PChar(FAddress));
    if FIPAddress <> LongInt(INADDR_NONE) then
        // Was a numeric dotted address let it in this format
        FHostName := FAddress
    else begin
        // Not a numeric dotted address, try to resolve by name
        Phe := GetHostByName(PChar(FAddress));
        if Phe = nil then begin
            FLastError := GetLastError;
            if Assigned(FOnDisplay) then
                FOnDisplay(Self, 'Unable to resolve ' + FAddress);
            Exit;
        end;

        FIPAddress := longint(plongint(Phe^.h_addr_list^)^);
        FHostName  := Phe^.h_name;
    end;

    FHostIP       := StrPas(inet_ntoa(TInAddr(FIPAddress)));
    FAddrResolved := TRUE;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
procedure TICMP.SetAddress(Value : String);
begin
    // Only change if needed (could take a long time)
    if FAddress = Value then
        Exit;
    FAddress      := Value;
    FAddrResolved := FALSE;
//    ResolveAddr;
end;


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function TICMP.GetErrorString : String;
begin
    case FLastError of
    IP_SUCCESS:               Result := 'No error';
    IP_BUF_TOO_SMALL:         Result := 'Buffer too small';
    IP_DEST_NET_UNREACHABLE:  Result := 'Destination network unreachable';
    IP_DEST_HOST_UNREACHABLE: Result := 'Destination host unreachable';
    IP_DEST_PROT_UNREACHABLE: Result := 'Destination protocol unreachable';
    IP_DEST_PORT_UNREACHABLE: Result := 'Destination port unreachable';
    IP_NO_RESOURCES:          Result := 'No resources';
    IP_BAD_OPTION:            Result := 'Bad option';
    IP_HW_ERROR:              Result := 'Hardware error';
    IP_PACKET_TOO_BIG:        Result := 'Packet too big';
    IP_REQ_TIMED_OUT:         Result := 'Request timed out';
    IP_BAD_REQ:               Result := 'Bad request';
    IP_BAD_ROUTE:             Result := 'Bad route';
    IP_TTL_EXPIRED_TRANSIT:   Result := 'TTL expired in transit';
    IP_TTL_EXPIRED_REASSEM:   Result := 'TTL expired in reassembly';
    IP_PARAM_PROBLEM:         Result := 'Parameter problem';
    IP_SOURCE_QUENCH:         Result := 'Source quench';
    IP_OPTION_TOO_BIG:        Result := 'Option too big';
    IP_BAD_DESTINATION:       Result := 'Bad Destination';
    IP_ADDR_DELETED:          Result := 'Address deleted';
    IP_SPEC_MTU_CHANGE:       Result := 'Spec MTU change';
    IP_MTU_CHANGE:            Result := 'MTU change';
    IP_GENERAL_FAILURE:       Result := 'General failure';
    IP_PENDING:               Result := 'Pending';
    else
        Result := 'ICMP error #' + IntToStr(FLastError);
    end;
end;


{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}
function TICMP.Ping : Integer;
var
  BufferSize:        Integer;
  pReqData, pData:   Pointer;
  pIPE:              PIcmpEchoReply;       // ICMP Echo reply buffer
  IPOpt:             TIPOptionInformation; // IP Options for packet to send
  Msg:               String;
begin
    Result     := 0;
    FLastError := 0;

    if not FAddrResolved then
        ResolveAddr;

    if FIPAddress = LongInt(INADDR_NONE) then begin
        FLastError := IP_BAD_DESTINATION;
        if Assigned(FOnDisplay) then
            FOnDisplay(Self, 'Invalid host address');
        Exit;
    end;

    // Allocate space for data buffer space
    BufferSize := SizeOf(TICMPEchoReply) + FSize;
    GetMem(pReqData, FSize);
    GetMem(pData,    FSize);
    GetMem(pIPE,     BufferSize);

    try
        // Fill data buffer with some data bytes
        FillChar(pReqData^, FSize, $20);
        Msg := 'Pinging from Delphi code written by F. Piette';
        Move(Msg[1], pReqData^, MinInteger(FSize, Length(Msg)));

        pIPE^.Data := pData;
        FillChar(pIPE^, SizeOf(pIPE^), 0);

        if Assigned(FOnEchoRequest) then
            FOnEchoRequest(Self);

        FillChar(IPOpt, SizeOf(IPOpt), 0);
        IPOpt.TTL   := FTTL;
        IPOpt.Flags := FFlags;
        Result      := IcmpSendEcho(hICMP, FIPAddress, pReqData, FSize,
                                    @IPOpt, pIPE, BufferSize, FTimeOut);
        FLastError  := GetLastError;
        FReply      := pIPE^;

        if Assigned(FOnEchoReply) then
            FOnEchoReply(Self, Result);
    finally
        // Free those buffers
        FreeMem(pIPE);
        FreeMem(pData);
        FreeMem(pReqData);
    end;
end;


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end.