Dear All! Helps on RSock::RecvFrom

Hi, I am working on a SE P900.

I designed to establish data transmission between many PCs and P900s using UDP.

Firstly, I tried to use Multicast, but it seems it's still a technology in developing, not being supported, so far. Am I wrong? Can some experienced developer correct me about this?

Then, I choose to use simple send and receive. There is no problem for me to send msg to PC at all. However, I cannot receive any msg from PC. The code is below
==================================

CUdpRead::CUdpRead() : CActive(EPriorityStandard)
{
}

CUdpRead* CUdpRead::NewL(RSocket* aSocket, CGameUi* aAppUi)
{
   CUdpRead* self = NewLC(aSocket, aAppUi);
   CleanupStack::Pop();
   return self;
}

CUdpRead* CUdpRead::NewLC(RSocket* aSocket, CGameUi* aAppUi)
{
   CUdpRead* self = new(ELeave) CUdpRead;
   CleanupStack::PushL(self);
   self->ConstructL(aSocket, aAppUi);
   return self;
}

void CUdpRead::ConstructL(RSocket* aSocket, CGameUi* aAppUi)
{
   // Open a UDP socket
   //User::LeaveIfError(iUdpSocket.Open(iSocketServ, KAfInet, KSockDatagram, KProtocolInetUdp));
   iUdpSocket = aSocket;   
   TInetAddr myLocalAddr;
   myLocalAddr.SetAddress(KInetAddrAny);
   myLocalAddr.SetPort(3025);
   User::LeaveIfError(iUdpSocket->Bind(myLocalAddr));
   User::InfoPrint(_L("UDP socket binded"));
   iAppUi      = aAppUi;
   CActiveScheduler::Add(this);
}

void CUdpRead::DoCancel()
{
   iUdpSocket->CancelRead();
}

void CUdpRead::IssueRead()         
{
   if (!IsActive())
   {
      TSockAddr anAddr;
      iUdpSocket->RecvFrom(iBuffer, anAddr, 0, iStatus);
      if(iStatus == KErrEof)
         User::InfoPrint(_L("UDP socket error"));
      else
      {
         User::InfoPrint(iStatusText);
      }
      SetActive();
   }
}

void CUdpRead::RunL()
{
   if (iStatus == KErrNone)   // Character has been read from socket
   {
      iStatusText.Copy(iBuffer);
      //User::InfoPrint(iStatusText);
      
      iAppUi->HandleIncomingPacket(iStatusText);
      
      IssueRead();
   }
   else
   {
      iStatusText=_L("\nError reading from socket");
      User::InfoPrint(iStatusText);
   }   
}
=========================================

There is no problem at either Bind() or construct the socket. No error msg at all.
Also, I put a User::InfoPrint() once any msg is received, it never happens.

So, could any friend help me about this?

It's said that, the phone is sitting behind router, which is applied by server. As a result, PC cannot get the actual IP of the phone. Hence, any data packets cannot be send to the correct IP address. If it's true, is there any easier way to help this case? I know that portmapping skills exist for PC, is there any for phone?

Thanks!

Regards
Chaosy