protected VeryLongInteger retrieveHashFromServer(BlockInfo bi) throws RetrievalException {
PartiallyReceivedBlock prb = new PartiallyReceivedBlock(Dijjer.PACKETS_IN_BLOCK, Dijjer.PACKET_SIZE);
HttpBlockReceiver hbr = new HttpBlockReceiver(bi, prb);
try {
hbr.start();
} catch (IOException e) {
throw new RetrievalException(RetrievalException.IO_ERROR, e.getMessage());
}
return new VeryLongInteger(prb.getBlock());
}