for ReceiveBuffer: 
  test := 1000000;
  Setsockopt(BroadCastReceive.HSocket, SOL_SOCKET , SO_RCVBUF, @test, SizeOf (test));
 and for SendBuffer:
  test := 1000000;
  Setsockopt(BroadSocket.HSocket, SOL_SOCKET , SO_SNDBUF, @test, SizeOf (test));

255.255.255.255

snippet 1 from wsocket.pas:

{$ELSE}
{$IFDEF VER120}
    { Delphi 4 has changed var parameters to pointers }
    FASocket := WSocket_accept(FHSocket, @sin, @len);
{$ELSE}
{$IFDEF VER125}
    { C++Builder 4 has changed var parameters to }
    { pointers (Added by James Legg)             }
    FASocket := WSocket_accept(FHSocket, @sin, @len);
{$ELSE}
    FASocket := WSocket_accept(FHSocket, TSockAddr(sin), len);
{$ENDIF}
{$ENDIF}

snippet 2 from tnemulvt

procedure TTnEmulVT.Connect;
var
{$IFDEF VER100}   { Delphi 3 }
    Form : TCustomForm;
{$ELSE}
{$IFDEF VER120}   { Delphi 4 }
    Form : TCustomForm;
{$ELSE}
{$IFDEF VER125}   { BCB4 Added by James Legg}
    Form : TCustomForm;
{$ELSE}
{$IFDEF VER110}   { BCB3 }
    Form : TCustomForm;
{$ELSE}
    Form : TForm;

function GetRASIPAddress: string;
var
  RASConns   : TRasConn;
  dwSize     : dword;
  dwCount    : dword;
  RASpppIP   : TRASpppIP;

Begin
  result          := '';
  RASConns.dwSize := SizeOf(TRASConn);
  RASpppIP.dwSize := SizeOf(RASpppIP);
  dwSize          := SizeOf(RASConns);

  If RASEnumConnections(@RASConns, @dwSize, @dwCount)=0 Then
      If dwCount > 0 Then begin
        dwSize := SizeOf(RASpppIP);
        If RASGetProjectionInfo(
            RASConns.hRasConn, RASP_PPPIP,
            @RasPPPIP, @dwSize) = 0 Then 
          result := strPas(RASpppIP.szIPAddress);
    End;
End;

var
   saddr       : TSockAddrIn;
   saddrlen    : Integer;
   AssignedPort: Word;
begin
   Sock.Addr := '0,0,0,0';
   Sock.Port   := '0'; // Listen on any port
   Sock.Listen;

   // Get the port assigned by winsock
   saddrlen := SizeOf(saddr);
   Sock.GetSockName(saddr, saddrlen);
   AssignedPort := WSocket_ntohs(saddr.sin_port);
end;

        XmtSocket->Multicast = true;
        XmtSocket->Proto = "udp";
        XmtSocket->Addr  = "225.1.2.3";  // or whatever you decide
        XmtSocket->Port  = 12345; // or whatever you decide
        XmtSocket->Connect();
        XmtSocket->Send(buf, size);
        XmtSocket->Close();

        RcvSocket->Proto             = "udp";
        RcvSocket->Addr              = "0.0.0.0";
        RcvSocket->MultiCast         = true;
        RcvSocket->ReuseAddr    = true;
        RcvSocket->Port              = 12345; // or whatever
        RcvSocket->MultiCastAddrStr  =225.1.2.3; // or whatever
        RcvSocket->Listen();

 Len = RcvSocket->ReceiveFrom(data, sizeof(data), Src, SrcLen);

     LineMode := True;
     LineEnd  := #13#10;

procedure TForm1.WSocket1Error(Sender: TObject);
begin
    with Sender as TWSocket do
         Log(WsocketErrorDesc(LastError));
end;

     LineMode := True;
     LineEnd  := #13#10;

type
   PTestRecord = ^TTestRecord;
   TTestRecord = packed record
     Ints : array[1..50] of integer;
   end;

  private
    WrPtr: integer;
    RdPtr: integer;
    Buffer: PChar;
    BufferSize: integer;

      RdPtr := 0;
      WrPtr := 0;
      if BufferSize = 0 then begin
         BufferSize := 16384;
         ReAllocMem(Buffer, BufferSize);
      end;

procedure TForm1.WSocket1DataAvailable(Sender: TObject; Error: Word);
var
   TR: PTestRecord;
   Count: integer;
begin
   if Error <> 0 then
      Exit;

   try
      if BufferSize - WrPtr <= 8192 then begin
         BufferSize := BufferSize * 2;
         ReAllocMem(Buffer, BufferSize);
      end;

      with Sender as TWSocket do
         Count := Receive(@Buffer[WrPtr], BufferSize - WrPtr);
      if Count <= 0 then
         Exit;

      Inc(WrPtr, Count);
      while WrPtr - RdPtr >= Sizeof(TTestRecord) do begin
         TR := @Buffer[RdPtr];
         ProcessData(TR);
         Inc(RdPtr, SizeOf(TTestRecord));
      end;

      if RdPtr = WrPtr then begin
         RdPtr := 0;
         WrPtr := 0;
      end;

   except
   end;
end;

procedure TForm1.WSocket1DataAvailable(Sender: TObject; Error: Word);
var
   TR: PTestRecord;
   Count: integer;
begin
   if Error <> 0 then begin
      Log('Winsock error: ' + IntToStr(Error));
      Exit;
   end;

   try
      if BufferSize - WrPtr <= 8192 then begin
         BufferSize := BufferSize * 2;
         ReAllocMem(Buffer, BufferSize);
      end;

      with Sender as TWSocket do
         Count := Receive(@Buffer[WrPtr], BufferSize - WrPtr);
      if Count <= 0 then
         Exit;

      Inc(WrPtr, Count);
      while WrPtr - RdPtr >= Sizeof(TTestRecord) do begin
         TR := @Buffer[RdPtr];
         ProcessData(TR);
         Inc(RdPtr, SizeOf(TTestRecord));
      end;

      if RdPtr = WrPtr then begin
         RdPtr := 0;
         WrPtr := 0;
      end;

   except
      on E: Exception do
         Log(E.Message);
   end;
end;

>
>  TSocketState       = (wsInvalidState,
>                        wsOpened,     wsBound,
>                        wsConnecting, wsConnected,
>                        wsAccepting,  wsListening,
>                        wsClosed);

procedure TForm1.SocketChangeState(
 Sender: Tobject; OldState, NewState: TSocketState);
const
    aWsState: array[TSocketState] of string = (
        'invalid',   'opened',    'bound',     'connecting',
        'connected', 'accepting', 'listening', 'closed'
  );
begin
    if not Application.Terminated then  // Dont forget this !!!
        Memo1.Lines.Add(aWsState[NewState]);
end;

Windows Sockets code	Error	Description
WSAEINTR	10004	Interrupted system call.
WSAEBADF	10009	Bad file number.
WSEACCES	10013	Permission denied.
WSAEFAULT	10014	Bad address.
WSAEINVAL	10022	Invalid argument.
WSAEMFILE	10024	Too many open files.
WSAEWOULDBLOCK	10035	Operation would block.
WSAEINPROGRESS	10036	Operation now in progress. This error is returned if any Windows Sockets API function is called while a blocking function is in progress.
WSAENOTSOCK	10038	Socket operation on nonsocket.
WSAEDESTADDRREQ	10039	Destination address required.
WSAEMSGSIZE	10040	Message too long.
WSAEPROTOTYPE	10041	Protocol wrong type for socket.
WSAENOPROTOOPT	10042	Protocol not available.
WSAEPROTONOSUPPORT	10043	Protocol not supported.
WSAESOCKTNOSUPPORT	10044	Socket type not supported.
WSAEOPNOTSUPP	10045	Operation not supported on socket.
WSAEPFNOSUPPORT	10046	Protocol family not supported.
WSAEAFNOSUPPORT	10047	Address family not supported by protocol family.
WSAEADDRINUSE	10048	Address already in use.
WSAEADDRNOTAVAIL	10049	Cannot assign requested address.
WSAENETDOWN	10050	Network is down. This error may be reported at any time if the Windows Sockets implementation detects an underlying failure.
WSAENETUNREACH	10051	Network is unreachable.
WSAENETRESET	10052	Network dropped connection on reset.
WSAECONNABORTED	10053	Software caused connection abort.
WSAECONNRESET	10054	Connection reset by peer.
WSAENOBUFS	10055	No buffer space available.
WSAEISCONN	10056	Socket is already connected.
WSAENOTCONN	10057	Socket is not connected.
WSAESHUTDOWN	10058	Cannot send after socket shutdown.
WSAETOOMANYREFS	10059	Too many references: cannot splice.
WSAETIMEDOUT	10060	Connection timed out.
WSAECONNREFUSED	10061	Connection refused.
WSAELOOP	10062	Too many levels of symbolic links.
WSAENAMETOOLONG	10063	File name too long.
WSAEHOSTDOWN	10064	Host is down.
WSAEHOSTUNREACH	10065	No route to host.
WSASYSNOTREADY	10091	Returned by WSAStartup(), indicating that the network subsystem is unusable.
WSAVERNOTSUPPORTED	10092	Returned by WSAStartup(), indicating that the Windows Sockets DLL cannot support this application.
WSANOTINITIALISED	10093	Winsock not initialized. This message is returned by any function except WSAStartup(), indicating that a successful WSAStartup() has not yet been performed.
WSAEDISCON	10101	Disconnect.
WSAHOST_NOT_FOUND	11001	Host not found. This message indicates that the key (name, address, and so on) was not found.
WSATRY_AGAIN	11002	Nonauthoritative host not found. This error may suggest that the name service itself is not functioning.
WSANO_RECOVERY	11003	Nonrecoverable error. This error may suggest that the name service itself is not functioning.
WSANO_DATA	11004	Valid name, no data record of requested type. This error indicates that the key (name, address, and so on) was not found.

You can find error code in winsock.hlp file. This file is available at ftp://ftp.stardust.com/sockets/wsa_dev.zip