[Synalist] UDP Multicast IP Address msb-lsb issue?

[Jon B. <Jo...@ci...>]

Hello,

We use DUnit on Delphi 2006/Windows XP to do automated unit tests on our =
code.  We updated from release 32 (I think) to release 37 and several =
UDP unit tests are now failing.

The unit tests are making sure that UDP multicast works.  The tests are =
failing because an attempt to AddMulticast('224.0.51.52') is returning =
with a winsock 10049 error (which is something like "address =
unavailable/invalid").

The DUnit code is:

 ...
  // set up UDP listener
  mxTestUDPSocket :=3D TUDPBlockSocket.Create;
  mxTestUDPSocket.Bind('0.0.0.0', C_SCRIPT_MULTICAST_PORT);
  mxTestUDPSocket.AddMulticast(C_SCRIPT_MULTI_CAST_BROADCAST_IP);
  Assert(mxTestUDPSocket.LastError =3D 0);
 ...

So the assert fails because LastError is 10049


THE OLD CODE:

Tracing into AddMulticast('224.0.51.52') with the code that works =
(release 32) shows it uses inet_addr()

procedure TUDPBlockSocket.AddMulticast(MCastIP: string);
begin
 ...
  Multicast.imr_multiaddr.S_addr :=3D synsock.inet_addr(PChar(MCastIP));
  Multicast.imr_interface.S_addr :=3D u_long(INADDR_ANY);
  SockCheck(synsock.SetSockOpt(FSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
    pchar(@Multicast), SizeOf(Multicast)));
 ...
end;

S_addr is 875757792.  I guess Windows must reverse the bits in the IP =
address because this is backwards.  Still, this is the case that works.


THE NEW CODE:

The new code uses a Synapse function to convert the IP dot notation to =
an integer.  This doesn't work:

procedure TUDPBlockSocket.AddMulticast(MCastIP: string);
begin
 ...
  Multicast.imr_multiaddr.S_addr :=3D strtoip(MCastIP);
  Multicast.imr_interface.S_addr :=3D INADDR_ANY;
  SockCheck(synsock.SetSockOpt(FSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
    pchar(@Multicast), SizeOf(Multicast)));
 ...
end;

S_addr is -536857804 (as an integer - or 3758109492 as an unsigned int).

This is what I'd expect 224.0.51.52 to convert to (224 is the most =
significate by I believe).  I'm assuming Intel big/little endian junk =
factors into the problem here.

There is a difference between new and old code.  New code doesn't work.  =
Is this a bug or did I miss something?


Jon B.