Prima della chiusura dell'handle attendi che i thread abbiano terminato il loro lavoro con la API WaitForMultipleObjects.
codice:
    //...
    HANDLE threadHandles[2];
    writeParams wp;
    //...
    threadHandles[0] = CreateThread(NULL, 0, WriteThreadProc, &wp, 0, NULL);
    //...
    readParams rp;
    //...
    threadHandles[1] = CreateThread(NULL, 0, ReadThreadProc, &rp, 0, NULL);
    //...
    WaitForMultipleObjects(2,threadHandles,TRUE,INFINITE);
    CloseHandle(threadHandles[0]);
    CloseHandle(threadHandles[1]);
    CloseHandle(hComm);