Qt 5.11 | Qt Network | Torrent Example | peerwireclient.cpp Example File

Qt 5.11.3 Reference Documentation

# peerwireclient.cpp Example File

torrent/peerwireclient.cpp

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      #include "peerwireclient.h"

      #include <QHostAddress>
      #include <QTimerEvent>

      static const int PendingRequestTimeout = 60 * 1000;
      static const int ClientTimeout = 120 * 1000;
      static const int ConnectTimeout = 60 * 1000;
      static const int KeepAliveInterval = 30 * 1000;
      static const int RateControlTimerDelay = 2000;
      static const int MinimalHeaderSize = 48;
      static const char ProtocolId[] = "BitTorrent protocol";
      static const char ProtocolIdSize = 19;

      // Reads a 32bit unsigned int from data in network order.
      static inline quint32 fromNetworkData(const char *data)
      {
          const unsigned char *udata = (const unsigned char *)data;
          return (quint32(udata[0]) << 24)
              | (quint32(udata[1]) << 16)
              | (quint32(udata[2]) << 8)
              | (quint32(udata[3]));
      }

      // Writes a 32bit unsigned int from num to data in network order.
      static inline void toNetworkData(quint32 num, char *data)
      {
          unsigned char *udata = (unsigned char *)data;
          udata[3] = (num & 0xff);
          udata[2] = (num & 0xff00) >> 8;
          udata[1] = (num & 0xff0000) >> 16;
          udata[0] = (num & 0xff000000) >> 24;
      }

      // Constructs an unconnected PeerWire client and starts the connect timer.
      PeerWireClient::PeerWireClient(const QByteArray &peerId, QObject *parent)
          : QTcpSocket(parent), pendingBlockSizes(0),
            pwState(ChokingPeer | ChokedByPeer), receivedHandShake(false), gotPeerId(false),
            sentHandShake(false), nextPacketLength(-1), pendingRequestTimer(0), invalidateTimeout(false),
            keepAliveTimer(0), torrentPeer(0)
      {
          memset(uploadSpeedData, 0, sizeof(uploadSpeedData));
          memset(downloadSpeedData, 0, sizeof(downloadSpeedData));

          transferSpeedTimer = startTimer(RateControlTimerDelay);
          timeoutTimer = startTimer(ConnectTimeout);
          peerIdString = peerId;

          connect(this, SIGNAL(readyRead()), this, SIGNAL(readyToTransfer()));
          connect(this, SIGNAL(connected()), this, SIGNAL(readyToTransfer()));

          connect(&socket, SIGNAL(connected()),
                  this, SIGNAL(connected()));
          connect(&socket, SIGNAL(readyRead()),
                  this, SIGNAL(readyRead()));
          connect(&socket, SIGNAL(disconnected()),
                  this, SIGNAL(disconnected()));
          connect(&socket, SIGNAL(error(QAbstractSocket::SocketError)),
                  this, SIGNAL(error(QAbstractSocket::SocketError)));
          connect(&socket, SIGNAL(bytesWritten(qint64)),
                  this, SIGNAL(bytesWritten(qint64)));
          connect(&socket, SIGNAL(stateChanged(QAbstractSocket::SocketState)),
                  this, SLOT(socketStateChanged(QAbstractSocket::SocketState)));

      }

      // Registers the peer ID and SHA1 sum of the torrent, and initiates
      // the handshake.
      void PeerWireClient::initialize(const QByteArray &infoHash, int pieceCount)
      {
          this->infoHash = infoHash;
          peerPieces.resize(pieceCount);
          if (!sentHandShake)
              sendHandShake();
      }

      void PeerWireClient::setPeer(TorrentPeer *peer)
      {
          torrentPeer = peer;
      }

      TorrentPeer *PeerWireClient::peer() const
      {
          return torrentPeer;
      }

      QBitArray PeerWireClient::availablePieces() const
      {
          return peerPieces;
      }

      QList<TorrentBlock> PeerWireClient::incomingBlocks() const
      {
          return incoming;
      }

      // Sends a "choke" message, asking the peer to stop requesting blocks.
      void PeerWireClient::chokePeer()
      {
          const char message[] = {0, 0, 0, 1, 0};
          write(message, sizeof(message));
          pwState |= ChokingPeer;

          // After receiving a choke message, the peer will assume all
          // pending requests are lost.
          pendingBlocks.clear();
          pendingBlockSizes = 0;
      }

      // Sends an "unchoke" message, allowing the peer to start/resume
      // requesting blocks.
      void PeerWireClient::unchokePeer()
      {
          const char message[] = {0, 0, 0, 1, 1};
          write(message, sizeof(message));
          pwState &= ~ChokingPeer;

          if (pendingRequestTimer)
              killTimer(pendingRequestTimer);
      }

      // Sends a "keep-alive" message to prevent the peer from closing
      // the connection when there's no activity
      void PeerWireClient::sendKeepAlive()
      {
          const char message[] = {0, 0, 0, 0};
          write(message, sizeof(message));
      }

      // Sends an "interested" message, informing the peer that it has got
      // pieces that we'd like to download.
      void PeerWireClient::sendInterested()
      {
          const char message[] = {0, 0, 0, 1, 2};
          write(message, sizeof(message));
          pwState |= InterestedInPeer;

          // After telling the peer that we're interested, we expect to get
          // unchoked within a certain timeframe; otherwise we'll drop the
          // connection.
          if (pendingRequestTimer)
              killTimer(pendingRequestTimer);
          pendingRequestTimer = startTimer(PendingRequestTimeout);
      }

      // Sends a "not interested" message, informing the peer that it does
      // not have any pieces that we'd like to download.
      void PeerWireClient::sendNotInterested()
      {
          const char message[] = {0, 0, 0, 1, 3};
          write(message, sizeof(message));
          pwState &= ~InterestedInPeer;
      }

      // Sends a piece notification / a "have" message, informing the peer
      // that we have just downloaded a new piece.
      void PeerWireClient::sendPieceNotification(int piece)
      {
          if (!sentHandShake)
              sendHandShake();

          char message[] = {0, 0, 0, 5, 4, 0, 0, 0, 0};
          toNetworkData(piece, &message[5]);
          write(message, sizeof(message));
      }

      // Sends the complete list of pieces that we have downloaded.
      void PeerWireClient::sendPieceList(const QBitArray &bitField)
      {
          // The bitfield message may only be sent immediately after the
          // handshaking sequence is completed, and before any other
          // messages are sent.
          if (!sentHandShake)
              sendHandShake();

          // Don't send the bitfield if it's all zeros.
          if (bitField.count(true) == 0)
              return;

          int bitFieldSize = bitField.size();
          int size = (bitFieldSize + 7) / 8;
          QByteArray bits(size, '\0');
          for (int i = 0; i < bitFieldSize; ++i) {
              if (bitField.testBit(i)) {
                  quint32 byte = quint32(i) / 8;
                  quint32 bit = quint32(i) % 8;
                  bits[byte] = uchar(bits.at(byte)) | (1 << (7 - bit));
              }
          }

          char message[] = {0, 0, 0, 1, 5};
          toNetworkData(bits.size() + 1, &message[0]);
          write(message, sizeof(message));
          write(bits);
      }

      // Sends a request for a block.
      void PeerWireClient::requestBlock(int piece, int offset, int length)
      {
          char message[] = {0, 0, 0, 1, 6};
          toNetworkData(13, &message[0]);
          write(message, sizeof(message));

          char numbers[4 * 3];
          toNetworkData(piece, &numbers[0]);
          toNetworkData(offset, &numbers[4]);
          toNetworkData(length, &numbers[8]);
          write(numbers, sizeof(numbers));

          incoming << TorrentBlock(piece, offset, length);

          // After requesting a block, we expect the block to be sent by the
          // other peer within a certain number of seconds. Otherwise, we
          // drop the connection.
          if (pendingRequestTimer)
              killTimer(pendingRequestTimer);
          pendingRequestTimer = startTimer(PendingRequestTimeout);
      }

      // Cancels a request for a block.
      void PeerWireClient::cancelRequest(int piece, int offset, int length)
      {
          char message[] = {0, 0, 0, 1, 8};
          toNetworkData(13, &message[0]);
          write(message, sizeof(message));

          char numbers[4 * 3];
          toNetworkData(piece, &numbers[0]);
          toNetworkData(offset, &numbers[4]);
          toNetworkData(length, &numbers[8]);
          write(numbers, sizeof(numbers));

          incoming.removeAll(TorrentBlock(piece, offset, length));
      }

      // Sends a block to the peer.
      void PeerWireClient::sendBlock(int piece, int offset, const QByteArray &data)
      {
          QByteArray block;

          char message[] = {0, 0, 0, 1, 7};
          toNetworkData(9 + data.size(), &message[0]);
          block += QByteArray(message, sizeof(message));

          char numbers[4 * 2];
          toNetworkData(piece, &numbers[0]);
          toNetworkData(offset, &numbers[4]);
          block += QByteArray(numbers, sizeof(numbers));
          block += data;

          BlockInfo blockInfo;
          blockInfo.pieceIndex = piece;
          blockInfo.offset = offset;
          blockInfo.length = data.size();
          blockInfo.block = block;

          pendingBlocks << blockInfo;
          pendingBlockSizes += block.size();

          if (pendingBlockSizes > 32 * 16384) {
              chokePeer();
              unchokePeer();
              return;
          }
          emit readyToTransfer();
      }

      // Attempts to write 'bytes' bytes to the socket from the buffer.
      // This is used by RateController, which precisely controls how much
      // each client can write.
      qint64 PeerWireClient::writeToSocket(qint64 bytes)
      {
          qint64 totalWritten = 0;
          do {
              if (outgoingBuffer.isEmpty() && !pendingBlocks.isEmpty()) {
                  BlockInfo block = pendingBlocks.takeFirst();
                  pendingBlockSizes -= block.length;
                  outgoingBuffer += block.block;
              }
              qint64 written = socket.write(outgoingBuffer.constData(),
                                            qMin<qint64>(bytes - totalWritten, outgoingBuffer.size()));
              if (written <= 0)
                  return totalWritten ? totalWritten : written;

              totalWritten += written;
              uploadSpeedData[0] += written;
              outgoingBuffer.remove(0, written);
          } while (totalWritten < bytes && (!outgoingBuffer.isEmpty() || !pendingBlocks.isEmpty()));

          return totalWritten;
      }

      // Attempts to read at most 'bytes' bytes from the socket.
      qint64 PeerWireClient::readFromSocket(qint64 bytes)
      {
          char buffer[1024];
          qint64 totalRead = 0;
          do {
              qint64 bytesRead = socket.read(buffer, qMin<qint64>(sizeof(buffer), bytes - totalRead));
              if (bytesRead <= 0)
                  break;
              qint64 oldSize = incomingBuffer.size();
              incomingBuffer.resize(oldSize + bytesRead);
              memcpy(incomingBuffer.data() + oldSize, buffer, bytesRead);

              totalRead += bytesRead;
          } while (totalRead < bytes);

          if (totalRead > 0) {
              downloadSpeedData[0] += totalRead;
              emit bytesReceived(totalRead);
              processIncomingData();
          }
          return totalRead;
      }

      // Returns the average number of bytes per second this client is
      // downloading.
      qint64 PeerWireClient::downloadSpeed() const
      {
          qint64 sum = 0;
          for (unsigned int i = 0; i < sizeof(downloadSpeedData) / sizeof(qint64); ++i)
              sum += downloadSpeedData[i];
          return sum / (8 * 2);
      }

      // Returns the average number of bytes per second this client is
      // uploading.
      qint64 PeerWireClient::uploadSpeed() const
      {
          qint64 sum = 0;
          for (unsigned int i = 0; i < sizeof(uploadSpeedData) / sizeof(qint64); ++i)
              sum += uploadSpeedData[i];
          return sum / (8 * 2);
      }

      void PeerWireClient::setReadBufferSize(qint64 size)
      {
          socket.setReadBufferSize(size);
      }

      bool PeerWireClient::canTransferMore() const
      {
          return bytesAvailable() > 0 || socket.bytesAvailable() > 0
              || !outgoingBuffer.isEmpty() || !pendingBlocks.isEmpty();
      }

      void PeerWireClient::connectToHost(const QHostAddress &address,
                                         quint16 port, OpenMode openMode)

      {
          setOpenMode(openMode);
          socket.connectToHost(address, port, openMode);
      }

      void PeerWireClient::diconnectFromHost()
      {
          socket.disconnectFromHost();
      }

      void PeerWireClient::timerEvent(QTimerEvent *event)
      {
          if (event->timerId() == transferSpeedTimer) {
              // Rotate the upload / download records.
              for (int i = 6; i >= 0; --i) {
                  uploadSpeedData[i + 1] = uploadSpeedData[i];
                  downloadSpeedData[i + 1] = downloadSpeedData[i];
              }
              uploadSpeedData[0] = 0;
              downloadSpeedData[0] = 0;
          } else if (event->timerId() == timeoutTimer) {
              // Disconnect if we timed out; otherwise the timeout is
              // restarted.
              if (invalidateTimeout) {
                  invalidateTimeout = false;
              } else {
                  abort();
                  emit infoHashReceived(QByteArray());
              }
          } else if (event->timerId() == pendingRequestTimer) {
              abort();
          } else if (event->timerId() == keepAliveTimer) {
              sendKeepAlive();
          }
          QTcpSocket::timerEvent(event);
      }

      // Sends the handshake to the peer.
      void PeerWireClient::sendHandShake()
      {
          sentHandShake = true;

          // Restart the timeout
          if (timeoutTimer)
              killTimer(timeoutTimer);
          timeoutTimer = startTimer(ClientTimeout);

          // Write the 68 byte PeerWire handshake.
          write(&ProtocolIdSize, 1);
          write(ProtocolId, ProtocolIdSize);
          write(QByteArray(8, '\0'));
          write(infoHash);
          write(peerIdString);
      }

      void PeerWireClient::processIncomingData()
      {
          invalidateTimeout = true;
          if (!receivedHandShake) {
              // Check that we received enough data
              if (bytesAvailable() < MinimalHeaderSize)
                  return;

              // Sanity check the protocol ID
              QByteArray id = read(ProtocolIdSize + 1);
              if (id.at(0) != ProtocolIdSize || !id.mid(1).startsWith(ProtocolId)) {
                  abort();
                  return;
              }

              // Discard 8 reserved bytes, then read the info hash and peer ID
              (void) read(8);

              // Read infoHash
              QByteArray peerInfoHash = read(20);
              if (!infoHash.isEmpty() && peerInfoHash != infoHash) {
                  abort();
                  return;
              }

              emit infoHashReceived(peerInfoHash);
              if (infoHash.isEmpty()) {
                  abort();
                  return;
              }

              // Send handshake
              if (!sentHandShake)
                  sendHandShake();
              receivedHandShake = true;
          }

          // Handle delayed peer id arrival
          if (!gotPeerId) {
              if (bytesAvailable() < 20)
                  return;
              gotPeerId = true;
              if (read(20) == peerIdString) {
                  // We connected to ourself
                  abort();
                  return;
              }
          }

          // Initialize keep-alive timer
          if (!keepAliveTimer)
              keepAliveTimer = startTimer(KeepAliveInterval);

          do {
              // Find the packet length
              if (nextPacketLength == -1) {
                  if (bytesAvailable() < 4)
                      return;

                  char tmp[4];
                  read(tmp, sizeof(tmp));
                  nextPacketLength = fromNetworkData(tmp);

                  if (nextPacketLength < 0 || nextPacketLength > 200000) {
                      // Prevent DoS
                      abort();
                      return;
                  }
              }

              // KeepAlive
              if (nextPacketLength == 0) {
                  nextPacketLength = -1;
                  continue;
              }

              // Wait with parsing until the whole packet has been received
              if (bytesAvailable() < nextPacketLength)
                  return;

              // Read the packet
              QByteArray packet = read(nextPacketLength);
              if (packet.size() != nextPacketLength) {
                  abort();
                  return;
              }

              switch (packet.at(0)) {
              case ChokePacket:
                  // We have been choked.
                  pwState |= ChokedByPeer;
                  incoming.clear();
                  if (pendingRequestTimer)
                      killTimer(pendingRequestTimer);
                  emit choked();
                  break;
              case UnchokePacket:
                  // We have been unchoked.
                  pwState &= ~ChokedByPeer;
                  emit unchoked();
                  break;
              case InterestedPacket:
                  // The peer is interested in downloading.
                  pwState |= PeerIsInterested;
                  emit interested();
                  break;
              case NotInterestedPacket:
                  // The peer is not interested in downloading.
                  pwState &= ~PeerIsInterested;
                  emit notInterested();
                  break;
              case HavePacket: {
                  // The peer has a new piece available.
                  quint32 index = fromNetworkData(&packet.data()[1]);
                  if (index < quint32(peerPieces.size())) {
                      // Only accept indexes within the valid range.
                      peerPieces.setBit(int(index));
                  }
                  emit piecesAvailable(availablePieces());
                  break;
              }
              case BitFieldPacket:
                  // The peer has the following pieces available.
                  for (int i = 1; i < packet.size(); ++i) {
                      for (int bit = 0; bit < 8; ++bit) {
                          if (packet.at(i) & (1 << (7 - bit))) {
                              int bitIndex = int(((i - 1) * 8) + bit);
                              if (bitIndex >= 0 && bitIndex < peerPieces.size()) {
                                  // Occasionally, broken clients claim to have
                                  // pieces whose index is outside the valid range.
                                  // The most common mistake is the index == size
                                  // case.
                                  peerPieces.setBit(bitIndex);
                              }
                          }
                      }
                  }
                  emit piecesAvailable(availablePieces());
                  break;
              case RequestPacket: {
                  // The peer requests a block.
                  quint32 index = fromNetworkData(&packet.data()[1]);
                  quint32 begin = fromNetworkData(&packet.data()[5]);
                  quint32 length = fromNetworkData(&packet.data()[9]);
                  emit blockRequested(int(index), int(begin), int(length));
                  break;
              }
              case PiecePacket: {
                  int index = int(fromNetworkData(&packet.data()[1]));
                  int begin = int(fromNetworkData(&packet.data()[5]));

                  incoming.removeAll(TorrentBlock(index, begin, packet.size() - 9));

                  // The peer sends a block.
                  emit blockReceived(index, begin, packet.mid(9));

                  // Kill the pending block timer.
                  if (pendingRequestTimer) {
                      killTimer(pendingRequestTimer);
                      pendingRequestTimer = 0;
                  }
                  break;
              }
              case CancelPacket: {
                  // The peer cancels a block request.
                  quint32 index = fromNetworkData(&packet.data()[1]);
                  quint32 begin = fromNetworkData(&packet.data()[5]);
                  quint32 length = fromNetworkData(&packet.data()[9]);
                  for (int i = 0; i < pendingBlocks.size(); ++i) {
                      const BlockInfo &blockInfo = pendingBlocks.at(i);
                      if (blockInfo.pieceIndex == int(index)
                          && blockInfo.offset == int(begin)
                          && blockInfo.length == int(length)) {
                          pendingBlocks.removeAt(i);
                          break;
                      }
                  }
                  break;
              }
              default:
                  // Unsupported packet type; just ignore it.
                  break;
              }
              nextPacketLength = -1;
          } while (bytesAvailable() > 0);
      }

      void PeerWireClient::socketStateChanged(QAbstractSocket::SocketState state)
      {
          setLocalAddress(socket.localAddress());
          setLocalPort(socket.localPort());
          setPeerName(socket.peerName());
          setPeerAddress(socket.peerAddress());
          setPeerPort(socket.peerPort());
          setSocketState(state);
      }

      qint64 PeerWireClient::readData(char *data, qint64 size)
      {
          int n = qMin<int>(size, incomingBuffer.size());
          memcpy(data, incomingBuffer.constData(), n);
          incomingBuffer.remove(0, n);
          return n;
      }

      qint64 PeerWireClient::readLineData(char *data, qint64 maxlen)
      {
          return QIODevice::readLineData(data, maxlen);
      }

      qint64 PeerWireClient::writeData(const char *data, qint64 size)
      {
          int oldSize = outgoingBuffer.size();
          outgoingBuffer.resize(oldSize + size);
          memcpy(outgoingBuffer.data() + oldSize, data, size);
          emit readyToTransfer();
          return size;
      }