Question

I use Indy 9 with Delphi 5. In my application I want to communicate with a network device via UDP. So I use UDPServer comp. in a class which is derived from TThread. When I write similar to the following code then CPU usage is 100%.

in the thread :

while not terminated do begin   if GetMessage(Msg, 0, 0, 0) then begin     if Msg.message = WM_UDPMSG then       Break     else       DispatchMessage(Msg);   end; end; 

and OnUDPRead event :

  try         // Processing the data here   except     PostThreadMessage(ThreadId, WM_UDPMSG, 0, 0);   end; 

When I use Sleep function in the while-do loop or in OnUDPRead event there is no change. Still the CPU usage is 100%.

My thread priority is Normal.

How can I solve my problem?

Answer 1

The problem you have is because you’re receiving the UDP data in the GUI thread, but want to process the data in another thread.

The real problem is that your trying to use a asynchronous component in a blocking way. The better solution would be to use a real blocking UDP communication library such as synapse. Then it’s very easy to just wait for new data to receive in your thread.

You could just write:

while not Terminated do begin   BytesRead := FSocker.RecvBufferEx(@(Buffer[0]), BufferSize, Timeout);   if (BytesRead = 0) then   begin     // continue or exit if the receiving Failed     case FSocket.LastError of       0, WSAETIMEDOUT: Continue;       WSAECONNRESET, WSAENETRESET,         WSAENOTCONN, WSAECONNABORTED,         WSAENETDOWN:         begin           CloseConnection;           Exit;         end;     else       CloseConnection;       Exit;     end;       end;   // process the data in the buffer end;