- Qt 5.5
- Qt Network
- Torrent Example
- peerwireclient.cpp Example File
- Qt 5.5.1 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;
    }