HINSTANCE hLib;
cfunc1 Init_TCP;
cfunc2 Close_TCP;
cfunc3 Get_TCPKey;
cfunc4 TCPTransfer;
cfunc5 Get_TCPDeviceName;
char mod[150];
int i;

UCHAR inBuffer[16];
READ_BUFFER* pinBuffer;
WRITE_BUFFER outBuffer;

boolean load_DLL() {
  BOOLEAN dll_ok;

  hLib = LoadLibrary("ITRA_DEVCOMM.dll");
  if (hLib != NULL) {
    dll_ok = TRUE;
    if (GetModuleFileName((HMODULE)hLib, (LPTSTR)mod, 150) == 0) dll_ok = FALSE;
    Init_TCP = (cfunc1)GetProcAddress((HMODULE)hLib,"Init_TCP");
    Close_TCP = (cfunc2)GetProcAddress((HMODULE)hLib,"Close_TCP");
    Get_TCPKey = (cfunc3)GetProcAddress((HMODULE)hLib,"Get_TCPKey");
    TCPTransfer = (cfunc4)GetProcAddress((HMODULE)hLib,"TCPTransfer");
    Get_TCPDeviceName = (cfunc5)GetProcAddress((HMODULE)hLib,"Get_TCPDeviceName");
  } else {
    dll_ok = FALSE;
  }
  if (Init_TCP == NULL) dll_ok = FALSE;
  if (Close_TCP == NULL) dll_ok = FALSE;
  if (Get_TCPKey == NULL) dll_ok = FALSE;
  if (TCPTransfer == NULL) dll_ok = FALSE;
  if (Get_TCPDeviceName == NULL) dll_ok = FALSE;

  return dll_ok;
}

...
  if (load_DLL() == TRUE) {                          // check the DLL
    if ((Init_TCP(0) & 0xFF00) == 0x3000) {          // check the usb driver, 0 = TCP-Controller
        
...
        
      // Code request and LED output
      // fill the writeBuffer with LED vars
      outBuffer[0] = ~(outBuffer[0]);
      outBuffer[1] = ~(outBuffer[1]);
      outBuffer[2] = ~(outBuffer[2]);
      outBuffer[3] = ~(outBuffer[3]);

      pinBuffer=TCPTransfer(&outBuffer);

/*
      // only Code request
      pinBuffer=Get_TCPKey();

*/

      if (pinBuffer->TransferResult == TRUE) {
        for (i=0;i<16;i++) {
          inBuffer[i]=pinBuffer->ReadBuffer[i];
        }
        // process the key events in inBuffer[3], inBuffer[4]

      } else {
        // Transfer Error
      }

      // the Module can be leaved open for loops, but close it on program end
      Close_TCP();
    } else {
      // Error Init
    }
  }