맨윗단에 있는 TSocket 에서 원하는 대로 지정해주면 될것 같은데여...
아래는 참고 소스 코드 임다...

-----------------------------------------------------------------
unit ListenThrd;

interface

uses
  Classes, ComCtrls, StdCtrls, Windows, Winsock2;


const

   BufferSize    = MAXGETHOSTSTRUCT;

type

TMCOptions = record
               Port      : Integer;
               Address   : String;
               UseWS2    : Boolean;
              end;

TConnData = record
              NumEvents : DWORD;
              EventArray : array[1..WSA_MAXIMUM_WAIT_EVENTS] of WSAEvent;
             end;

TMulticast = record
               imr_multiaddr : TInAddr;   // IP multicast address of group */
               imr_interface : TInAddr;   // local IP address of interface */
              end;

  TListenThrd = class(TThread)
  private
    { Private declarations }
   FRunning : Boolean;
  protected
    MsgNo                  : Integer;
    EventMsg               : WSAEVENT;
    lpNetworkEvents        : PWSANETWORKEVENTS;
    ConnData               : TConnData;
    Buffers                : array[0..BufferSize - 1] of char;
    Msg,
    StatusMsg              : String;
    Done                   : Boolean;
    ReUseFlag              : BOOL;
    sktBlast               : TSocket;
    Multicast              : TMulticast;
    MCOptions              : TMCOptions;
    LocalAddr,
    RemoteAddr             : TSockAddr;
    Started                : Boolean;
    wsaData                : TWSADATA;
    function Start : Boolean;
    procedure DisplayMsg;
    procedure DisplayStatusMsg;
    procedure ChangeWS;
    procedure ChangeBtnState;
    procedure CleanUp(Sender : TObject);
    procedure HandleSocketEvent;
    procedure GetMsg;
    function  JoinSession : Boolean;
    procedure LeaveSession;
    procedure Execute; override;
  public
    property Running : Boolean read FRunning default FALSE;
    procedure CloseSession;
    constructor Create(Options : TMCOptions);
  end;

var
thrdListen : TListenThrd;
Options    : TMCOptions;

implementation
{ TListenThrd }

Uses
Dialogs, Forms, Main, SysUtils;

var
  AddrStrSize   : Integer;

function TListenThrd.Start : Boolean;
var
VerReqd : WordRec;
begin
with VerReqd do
begin
  Hi := 2;
  Lo := 2;
end;
Result := WSAStartUp(Word(VerReqd), wsaData) = 0;
end;

procedure TListenThrd.DisplayMsg;
begin
  frmMain.memMsg.Lines.Add(Msg);
end;

procedure TListenThrd.DisplayStatusMsg;
begin
frmMain.memStatusMsg.Lines.Add(StatusMsg);
end;

procedure TListenThrd.ChangeWS;
begin
MessageBeep(0);
with frmMain do
  WindowState := wsNormal;
end;

procedure TListenThrd.ChangeBtnState;
begin
frmMain.bbtnStop.Enabled  := not frmMain.bbtnStop.Enabled;
frmMain.bbtnStart.Enabled := not frmMain.bbtnStart.Enabled;
end;


procedure TListenThrd.CleanUp(Sender : TObject);
begin
if Started then
begin
  closesocket(sktBlast);
  WSACleanUp;
end;
end;

function TListenThrd.JoinSession : Boolean;
var
sktRes : Integer;
sktTemp : TSocket;
begin
Result := TRUE;
case MCOptions.UseWS2 of
  TRUE :  begin
           sktTemp := WSAJoinLeaf(sktBlast, @RemoteAddr, SizeOf(RemoteAddr), NIL, NIL, NIL, NIL, JL_RECEIVER_ONLY);
           if sktTemp = INVALID_SOCKET then
           begin        
            StatusMsg := Concat('Call to WSAJoinLeaf failed! Error ', IntToStr(WSAGetLastError));
            Synchronize(DisplayStatusMsg);
            Result := FALSE;
            Synchronize(ChangeBtnState);
            Exit;
           end;
          end;
  FALSE : begin
           with Multicast do
           begin
            imr_multiaddr.s_addr := inet_addr(PChar(MCOptions.Address));
            imr_interface.s_addr := INADDR_ANY;
           end;
           sktRes := setsockopt(sktBlast,IPPROTO_IP, IP_ADD_MEMBERSHIP, pchar(@Multicast), SizeOf(Multicast));
           if sktRes = SOCKET_ERROR then
           begin
            StatusMsg := Concat('Call to setsockopt failed! Error ', IntToStr(WSAGetLastError));
            Synchronize(DisplayStatusMsg);
            Result := FALSE;
           end;
          end;
end;// case
end;

procedure TListenThrd.LeaveSession;
var
sktRes : Integer;
begin
if not UseWS2 then
  with Multicast do
  begin
   imr_multiaddr.s_addr := inet_addr(MultiCastAddr);
   imr_interface.s_addr := INADDR_ANY;
  end;
  sktRes := setsockopt(sktBlast, IPPROTO_IP, IP_DROP_MEMBERSHIP, pchar(@Multicast), SizeOf(Multicast));
  if sktRes = SOCKET_ERROR then
  begin
   StatusMsg := Concat('Call to setsockopt failed! Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
  end;
end;

procedure TListenThrd.CloseSession;
begin
// Leave session ...
LeaveSession;
// Terminate the thread by setting the global Done and call
Done := TRUE;
// Call WSASetEvent to signal HandleSocketEvent
WSASetEvent(EventMsg);
end;

constructor TListenThrd.Create(Options : TMCOptions);
var
sktRes : Integer;
begin
inherited Create(TRUE);
MCOptions := Options;
FreeOnTerminate := TRUE;
Started := Start;
if not Started then
begin
  StatusMsg := 'Cannot load Winsock 2.0!';
  Synchronize(DisplayStatusMsg);
  Exit;
end;
OnTerminate := CleanUp;
MsgNo := 0;
with MCOptions do
begin
// get a UDP socket
  if UseWS2 then
  begin
// Convert address string to a value
   RemoteAddr.sin_family := AF_INET;
   AddrStrSize := 16;
   sktRes := WSAStringToAddress(Pchar(MultiCastAddr),AF_INET, NIL, @RemoteAddr, @AddrStrSize);
   if sktRes = SOCKET_ERROR then
   begin
    StatusMsg := Concat('Call to WSAStringToAddress failed! Error ', IntToStr(WSAGetLastError));
    Synchronize(DisplayStatusMsg);
    Exit;
   end;
   sktBlast := WSASocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP, NIL, 0, WSA_FLAG_OVERLAPPED or
                         WSA_FLAG_MULTIPOINT_C_LEAF or
                         WSA_FLAG_MULTIPOINT_D_LEAF);
  end
  else
   sktBlast := socket(AF_INET, SOCK_DGRAM, 0);
  if sktBlast = SOCKET_ERROR then
  begin
   StatusMsg := Concat('Failed to create UDP socket! Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
   Exit;
  end;
// Create an event ...
  EventMsg := CreateEvent(NIL, FALSE, FALSE, NIL);
  if EventMsg = WSA_INVALID_EVENT then
  begin
   StatusMsg := Concat('Failed to create Message Event. Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
   Done := TRUE;
   Exit;
  end;
// Now set up notification ...
  sktRes := WSAEventSelect(sktBlast, EventMsg, FD_READ);
  if sktRes = SOCKET_ERROR then
  begin
   StatusMsg := Concat('Call to WSAEventSelect failed for socket ', IntToStr(sktBlast),'. Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
   closesocket(sktBlast);
   Done := TRUE;
   Exit;
  end;
// Set up socket options for multicast ...
// Always reuse socket
  ReUseFlag := TRUE;
  sktRes := setsockopt(sktBlast, SOL_SOCKET, SO_REUSEADDR, @ReUseFlag,
                       SizeOf(ReUseFlag));
  if sktRes = SOCKET_ERROR then
  begin
   StatusMsg := Concat('Call to setsockopt failed! Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
   closesocket(sktBlast);
   Synchronize(ChangeWS);
   Exit;
  end;
// Name the socket and assign the local port number to receive on
  with LocalAddr do
  begin
   sin_family      := AF_INET;
   sin_addr.s_addr := htonl(INADDR_ANY);
   sin_port        := htons(MCOptions.Port);
  end;
// bind it!
  sktRes := bind(sktBlast, LocalAddr, SizeOf(TSockAddrIn));
  if sktRes = SOCKET_ERROR then
  begin
   StatusMsg := Concat('Call to bind failed ! Error ', IntToStr(WSAGetLastError));
   Synchronize(DisplayStatusMsg);
   closesocket(sktBlast);
   Exit;
  end;
  if UseWS2 then
  begin
// swap host to network order ...
   with RemoteAddr do
   begin
    sin_family := PF_INET;
    sktRes := WSAHtons(sktBlast, MCOptions.Port, @sin_port);
    if sktRes = SOCKET_ERROR then
    begin
     StatusMsg := Concat('Call to WSAHtons failed! Error ', IntToStr(WSAGetLastError));
     Synchronize(DisplayStatusMsg);
     closesocket(sktBlast);
     Exit;
    end;
   end;
  end;
// Join the multicast group
  if not JoinSession then
  begin
   closesocket(sktBlast);
   Exit;
  end;
  StatusMsg := 'Started listening thread ...';
  Synchronize(DisplayStatusMsg);
end;// with MCOptions
Resume;
end;

procedure TListenThrd.HandleSocketEvent;
var
sktRes : Integer;
begin
sktRes := WSAEnumNetworkEvents(sktBlast, EventMsg, @Buffers[0]);
if sktRes = SOCKET_ERROR then
begin
  StatusMsg := Concat('Call to WSAEnumNetworkEvents failed. Error ',IntToStr(WSAGetLastError));
  Synchronize(DisplayStatusMsg);
  Done := TRUE;
  Exit;
end;
lpNetworkEvents := PWSANETWORKEVENTS(@Buffers[0]);
// Decipher network events ...
with lpNetworkevents^ do
begin
// Is this a FD_READ event?
  if (lNetworkEvents and FD_READ) = FD_READ then
  begin
   if iErrorCode[1] = WSAENETDOWN then
   begin
    StatusMsg := Concat('Network down ... Error ',IntToStr(WSAGetLastError));
    Synchronize(DisplayStatusMsg);
   end else
   begin
    GetMsg;
   end;
  end;
end;
end;

procedure TListenThrd.GetMsg;
var
Error: Integer;
Buff : PWSABUF;
Flags, NoBytes,
Size,
sktRes,
AddrStrSize : Integer;
AddrStr : array[0..MAXGETHOSTSTRUCT - 1] of char;
PortNo : shortint;

begin
// Get the message ...
Buff := NIL;
Flags := 0;
AddrStrSize := MAXGETHOSTSTRUCT;
try
  Buff       := AllocMem(SizeOf(Buffers));
  Buff.Buf   := Buffers;
  Buff.len   := SizeOf(Buffers);
  Size       := SizeOf(RemoteAddr);
  sktRes     := WSARecvFrom(sktBlast, Buff, 1, @NoBytes, @Flags, @RemoteAddr, @Size, NIL, NIL);
  if sktRes = SOCKET_ERROR then
  begin
   Error := WSAGetLastError;
   if Error <> WSAEWOULDBLOCK then
   begin
    StatusMsg := Concat('Call to WSARecvFrom failed! Error ', IntToStr(WSAGetLastError));
    Synchronize(DisplayStatusMsg);
    Done := TRUE;
    WSASetEvent(EventMsg);
   end;
  end else
  begin
   Synchronize(ChangeWS);
   Msg := String(Buff.buf);
   Synchronize(DisplayMsg);
// Convert address to a readable string ...
   PortNo := 0;
   sktRes := WSAAddressToString(@RemoteAddr, SizeOf(RemoteAddr), NIL, AddrStr, @AddrStrSize);
   if sktRes = SOCKET_ERROR then
   begin
    StatusMsg := Concat('Call to WSAAddressToString failed! Error ', IntToStr(WSAGetLastError));
    Synchronize(DisplayStatusMsg);
   end;
// Convert from network to host byte order
   sktRes := WSANtohs(sktBlast,RemoteAddr.sin_port, @PortNo);
   if sktRes = SOCKET_ERROR then
   begin
    StatusMsg := Concat('Call to WSANtohs failed! Error ', IntToStr(WSAGetLastError));
    Synchronize(DisplayStatusMsg);
   end else
   begin
    StatusMsg := Concat('Message #', IntToStr(MsgNo), ' received from ', String(AddrStr));
    Synchronize(DisplayStatusMsg);
   end;
  end;
finally
  FreeMem(Buff);
end;
end;


procedure TListenThrd.Execute;
var
WaitStatus : DWORD;
begin
with ConnData do
begin
  NumEvents := 1;
  EventArray[1] := EventMsg;
  Done := FALSE;
  repeat
   WaitStatus := WSAWaitForMultipleEvents(NumEvents, @EventArray, FALSE, WSA_INFINITE, FALSE);
   case WaitStatus of
    WSA_WAIT_FAILED    : begin
                          StatusMsg := Concat('WSA_WAIT_FAILED ... Error ',IntToStr(WSAGetLastError));
                          Synchronize(DisplayStatusMsg);
                          Done := TRUE;
                         end;
    WAIT_IO_COMPLETION : begin
                          StatusMsg := 'WAIT_IO_COMPLETION ...';
                          Synchronize(DisplayStatusMsg);
                         end;
    WSA_WAIT_EVENT_0   : begin
                          StatusMsg := 'WSA_WAIT_EVENT_0 ...';
                          Synchronize(DisplayStatusMsg);
                          if Done then
                          begin// then we are done ...
                           StatusMsg := 'Listening thread terminated ...';
                           Synchronize(DisplayStatusMsg);
                          end else
                          begin
                           Inc(MsgNo);
                           HandleSocketEvent;
                          end;
                         end;
   end;// case
  until Done;
end;
end;

end.

안녕하세욤!

UDP는 통신용으로는 적합하지 않다고 생각 합니다.
그래서 요즘 TCP/IP를 쓰는것이

UDP는 무조건 보내는 형태이라서 중간에 패킷이 손실 되면
찾을 길이 없습니다. -.-  이를 보안 한것이 TCP/IP로 알고 있거든요
TCP/IP는 한 패킷을 보내고, 받은쪽에서 받았다고 메세지가 오면
다시 한패킷 보내고 이런식인데 반해

UDP는 말 그대로 주~~~욱 보내는거라 중간에 어떤 패킷이 손실 됬는지
찾기가 무척 힙듭니다..
(고수님들 맞죠? ^^;;)

해서 보통 UDP는 음성 전달용으로 사용 많이 하죠. 음성은 패킷 잃어버려도
큰 지장이 없지만 바이너리 데이터는 한 패킷만 없어도 CRC에러가 발생합니다


참고로 FastNet에 있는 UDP는 간단하며, 클라이언트/서버 역활 다 합니다.
Local Port하고 Remote Port를 같은 값으로 주시고 Remote Host에 아이피를
적어주시면 됩니다.

하나더 참고로 인디에서 제공하는 UDP는 서버/클라이언트 구분 합니다.


그리고 진짜 마지막 -0-
멀티 태스크 말씀 하시는거 같은데욤.. TCP/IP가 낳을듯 하네요 ^^

즐코 되세욤!!

저녁에 글을 올렸는데 아침에 답변을 보게 되네요.. 답변 감사합니다..^^
근데 제가 몇 가지 빠트린 것이 있군요..
우선 제가 할려고 하는 부분은 Client 쪽임다.. Server 쪽은 이미 만들어져 있죠

UNIX OS 이구여.. 근데 Server 자료가 UDP로 옵니다..물론 님의 말씀이 틀린것은 아닙니다만 굳이 UDP를 쓴이유에 대해서는 제가 Server 쪽 담당이 아니라 별로 드릴 말씀이 없군여 ..중요한 것은 이 Server 쪽에서 멀티캐스팅으로 자룔 뿌린 다는거죠..물론 같은 OS 군으로 Client 는 만들어져 있습니다.

같은 OS 환경상에서는 큰 문제 없이 작동하겠죠..문제는 제가 이걸 일반 windows 환경의 PC로 받아서 자료를 처리하고 싶더군요..근데 문제가 생기더군요..Demos 디렉토리의 UDP 통신예제에서 IP 는 멀티 그룹 IP를 주고 PORT는 물론 정해진 것을 줬죠..그랬더니 error 가 뜨더군요..물론 PC routing table에는 멀티캐스팅 그룹이 등록되있슴다..

그래서 제가 생각해보건데(제 짧은생각이자만) UNIX 에서 UDP 소켓을 생성하고 멀티캐스팅할때 옵션을 준다는 거죠..아래와 같이요

int np_create_multicast_inbound_socket (int                port,
                                        unsigned int       ip_group_addr,
                                        unsigned int       local_ip_addr,
                                        int                max_rx_size,
                                        struct sockaddr_in *udp_socket,
                                        int                *err_no)
{

  int                          fd;
  int                          s;
  int                          max_buffer_size;
  struct ip_mreq               mreq;

  max_buffer_size = max_rx_size;

  /* Create inbound socket */

  fd = socket (AF_INET, SOCK_DGRAM, 0);

  if (fd == NP_ERR) {
    *err_no = errno;
    np_log_errno ("socket()", "np_create_multicast_inbound_socket",
                errno);
    return (NP_ERR);
  }

  /* Set maximum receive buffer size. */

  if (max_rx_size == NP_DEFAULT) {
    /* noop, continue */
  }
  else {

    s = setsockopt (fd, SOL_SOCKET, SO_RCVBUF,
                    &max_buffer_size, sizeof(max_buffer_size));

    if (s == NP_ERR) {
      np_log_errno ("setsockopt(), SO_RCVBUF",
                    "np_create_multicast_inbound_socket", errno);
      np_log_info ("CONTINUE", "np_create_multicast_inbound_socket");
    }
  }

  memset (udp_socket, 0, sizeof (struct sockaddr_in));

  /* Join multicast group.   */
  /* Setup interface address */

  udp_socket->sin_port         = port;
  udp_socket->sin_family       = AF_INET;
  udp_socket->sin_addr.s_addr  = ip_group_addr;

  memset (&mreq, 0, sizeof (struct ip_mreq));

  mreq.imr_multiaddr.s_addr    = ip_group_addr;
  mreq.imr_interface.s_addr    = local_ip_addr;

  setsockopt(fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));

  if (s == NP_ERR) {
    *err_no = errno;
    np_log_errno ("setsockopt(), IP_ADD_MEMBERSHIP",
                  "np_create_multicast_inbound_socket", errno);
    np_shutdown_socket (fd);
    return (NP_ERR);
  }

  /* Bind multicast address and port number. */

  s = bind (fd, (void *) udp_socket, sizeof (struct sockaddr_in));

  if (s == NP_ERR) {
    *err_no = errno;
    np_log_errno ("bind()", "np_create_multicast_inbound_socket", errno);
    np_shutdown_socket (fd);
    return (NP_ERR);
  }

  *err_no = 0;

  if (tracing_on) {
    sprintf (trace_msg, "SUCCESS GROUP Addr: %s Port: %d",
             np_inet_ntoa(ip_group_addr), udp_socket->sin_port);
    np_log_trace (trace_msg, "np_create_multicast_inbound_socket()");
  }

  return (fd);

}

(죄송함다..델파이 게시판에 C 를 써서..--;;)

근데 이러한 것들을 UDP 컴포넌트에서는 어떻게 안되겠더군여...
그래서 혹 아시는 분이 있나해서 여쭤 본겁니다. 그 Componet 가 님께서
얘기하신 작용외에 어떤 추가적인 부분을 할수 없다면 별수 없이 winsock 을
써야 겠군여..아무튼 답변 감사합니다..