How to send a file in Qt?

问题

I'm trying to send a file from client to server. But it sends only a part of file. Seems like it happens when the size of file is more than 2Mb. What can be the problem? Sorry if it's a stupid question but I can't find an answer in Google.

This is client cpp:

#include "widget.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    progressBar = new QProgressBar(this);

    tcpSocket = new QTcpSocket(this);

    fileLabel = new QLabel(this);
    progressLabel = new QLabel(this);

    fileBtn = new QPushButton(this);
    fileBtn->setText("Open");

    sendBtn = new QPushButton(this);
    sendBtn->setText("Send");

    layout = new QGridLayout;
    layout->addWidget(fileBtn, 0, 0);
    layout->addWidget(sendBtn, 0, 1);
    layout->addWidget(fileLabel, 1, 0);
    layout->addWidget(progressBar, 2, 0);

    connect(fileBtn, &QPushButton::clicked, this, &Widget::fileOpened);
    connect(sendBtn, &QPushButton::clicked, this, &Widget::onSend);

    setLayout(layout);
}

Widget::~Widget()
{
}

void Widget::fileOpened()
{
    fileName = QFileDialog::getOpenFileName(this, tr("Open file"));
    QFileInfo fileInfo(fileName);
    fileLabel->setText(fileInfo.fileName() + " : " + QString::number(fileInfo.size()));
    qDebug() << fileName;
}

void Widget::onSend()
{
    tcpSocket->connectToHost("127.0.0.1", 33333);
    QFile file(fileName);

    QDataStream out(tcpSocket);
    int size = 0;

    if (file.open(QIODevice::ReadOnly))
    {
        QFileInfo fileInfo(file);
        QString fileName(fileInfo.fileName());

        out << fileName;
        qDebug() << fileName;
        out << QString::number(fileInfo.size());
        qDebug() << fileInfo.size();

        progressBar->setMaximum(fileInfo.size());

        while (!file.atEnd())
        {
            QByteArray rawFile;
            rawFile = file.read(5000);
            //false size inc
            QFileInfo rawFileInfo(rawFile);
            size += rawFileInfo.size();
            out << rawFile;
            progressBar->setValue(rawFile.size());
            qDebug() << QString::number(fileInfo.size());
            qDebug() << "ToSend:"<< rawFile.size();
        }
        out << "#END";
    }
}

This is a server one:

#include "myserver.h"


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    startBtn = new QPushButton(this);
    startBtn->setText("Connect");

    progressBar = new QProgressBar(this);

    layout = new QGridLayout;
    layout->addWidget(startBtn, 0, 0);
    layout->addWidget(progressBar, 1, 0);

    connect(startBtn, &QPushButton::clicked, this, &MainWindow::on_starting_clicked);

    setCentralWidget (new QWidget (this));
    centralWidget()->setLayout(layout);
}

MainWindow::~MainWindow()
{
    server_status=0;
}

void MainWindow::on_starting_clicked()
{
    startBtn->setText("Connecting...");
    tcpServer = new QTcpServer(this);
    connect(tcpServer, SIGNAL(newConnection()), this, SLOT(acceptConnection()));
    if (!tcpServer->listen(QHostAddress::Any, 33333) && server_status==0)
    {
        qDebug() <<  QObject::tr("Unable to start the server: %1.").arg(tcpServer->errorString());
    }
    else
    {
        server_status=1;
        qDebug() << QString::fromUtf8("Сервер запущен!");
        startBtn->setText("Running");
    }
}

void MainWindow::acceptConnection()
{

    qDebug() << QString::fromUtf8("У нас новое соединение!");
    tcpServerConnection = tcpServer->nextPendingConnection();
    connect(tcpServerConnection,SIGNAL(readyRead()),this, SLOT(slotReadClient()));
    // tcpServer->close();

    QDir::setCurrent("/Users/vlad/Desktop/");
    QString fileName;
    QString fileSize;

}


void MainWindow::slotReadClient()
{
    QDataStream in(tcpServerConnection);
    QByteArray z;

    if (!isInfoGot)
    {
        isInfoGot = true;
        in >> fileName;
        qDebug() << fileName;
        in >> fileSize;
        qDebug() << fileSize;
    }
    QFile loadedFile(fileName);

    if (loadedFile.open(QIODevice::Append))
    {
        while (tcpServerConnection->bytesAvailable())
        {
            qDebug() << "bytesAvailable:" << tcpServerConnection->bytesAvailable();
            in >> z;
            qDebug() << z;
            loadedFile.write(z);

        }
        loadedFile.close();
    }
}

回答1:

Not so far i faced the same problem. So i find some solution. Test it on files about ~200Mb, no problems i see.

Sender part:

void FileSender::send()
{
    QTcpSocket *socket = new QTcpSocket;

    connect(socket, SIGNAL(disconnected()), socket, SLOT(deleteLater()));

    // specified m_host and m_port to yours
    socket->connectToHost(m_host, m_port);
    socket->waitForConnected();

    if ( (socket->state() != QAbstractSocket::ConnectedState) || (!m_file->open(QIODevice::ReadOnly)) ) {
        qDebug() << "Socket can't connect or can't open file for transfer";
        delete socket;
        return;
    }

    QByteArray block;
    QDataStream out(&block, QIODevice::WriteOnly);
    out.setVersion(QDataStream::Qt_5_4);

    // This part i  need to send not only file, but file name too
    // Erase it if you needn't it 
    out << (quint32)0 << m_file->fileName();

    QByteArray q = m_file->readAll();
    block.append(q);
    m_file->close();

    out.device()->seek(0);
    // This difference appear because of we send file name
    out << (quint32)(block.size() - sizeof(quint32));

    qint64 x = 0;
    while (x < block.size()) {
        qint64 y = socket->write(block);
        x += y;
        //qDebug() << x;    // summary size you send, so you can check recieved and replied sizes
    }
}

Server part:

I specified my server as :

class Server : public QTcpServer
{
    Q_OBJECT
public:
    explicit Server(QHostAddress host = QHostAddress::Any,
                    quint16 port      = Constants::Server::DEFAULT_PORT,
                    QObject *parent   = 0);
    ~Server();

public slots:
    void start();

protected:
    void incomingConnection(qintptr handle) Q_DECL_OVERRIDE;

private:
    QHostAddress m_host;
    quint16      m_port;
};

And realization:

Server::Server(QHostAddress host, quint16 port, QObject *parent)
    : QTcpServer(parent),
      m_host(host),
      m_port(port)
{
    ...
    // your settings init there
}

void Server::start()
{
    if ( this->listen(m_host, m_port) )
        qDebug() << "Server started at " << m_host.toString() << ":" << m_port;
    else
        qDebug() << "Can't start server";
}

void Server::incomingConnection(qintptr handle)
{
    qDebug() << "incomingConnection = " << handle;
    SocketThread *thread = new SocketThread(handle);
    connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));

    thread->start();
}

As you can see i create new class SocketThread for receiving as multitheading server i need.

class SocketThread : public QThread
{
    Q_OBJECT
public:
    SocketThread(qintptr descriptor, QObject *parent = 0);
    ~SocketThread();

protected:
    void run() Q_DECL_OVERRIDE;

signals:
    void onFinishRecieved();

private slots:
    void onReadyRead();
    void onDisconnected();

private:
    qintptr     m_socketDescriptor;
    QTcpSocket *m_socket;
    qint32      m_blockSize;
};


SocketThread::SocketThread(qintptr descriptor, QObject *parent)
    : QThread(parent),
      m_socketDescriptor(descriptor),
      m_blockSize(0)
{
}

SocketThread::~SocketThread()
{
    delete m_socket;
}

void SocketThread::run()
{
    m_socket = new QTcpSocket;
    m_socket->setSocketDescriptor(m_socketDescriptor);

    connect(m_socket, SIGNAL(readyRead()),    this, SLOT(onReadyRead()),    Qt::DirectConnection);
    connect(m_socket, SIGNAL(disconnected()), this, SLOT(onDisconnected()), Qt::DirectConnection);

    exec();
}

void SocketThread::onReadyRead()
{
    QDataStream in(m_socket);
    in.setVersion(QDataStream::Qt_5_4);

    if (m_blockSize == 0) {
        if (m_socket->bytesAvailable() < sizeof(quint32))
        return;
        in >> m_blockSize;
    }
    if (m_socket->bytesAvailable() < m_blockSize)
        return;

    QString fileName;
    // get sending file name
    in >> fileName;
    QByteArray line = m_socket->readAll();

    QString filePath = "YOUR"; // your file path for receiving  
    fileName = fileName.section("/", -1);
    QFile target(filePath + "/" + fileName);

    if (!target.open(QIODevice::WriteOnly)) {
        qDebug() << "Can't open file for written";
        return;
    }
    target.write(line);

    target.close();

    emit onFinishRecieved();
    m_socket->disconnectFromHost();
}

void SocketThread::onDisconnected()
{
    m_socket->close();

    // leave event loop
    quit();
}

I hope you will be able to adapt my code to your project. Best regards

回答2:

Vlad, I'd suggest you to look at a Qt Example, like this one: http://doc.qt.io/qt-5/qtbluetooth-btfiletransfer-example.html

Just ignore the BT specific stuff, and see what it do.

I think I can help you more if I had a stand-alone code, which I could compile... ie, you didn't posted the headers, main files, and so. Make a zip, up it somewhere, and I can try looking what is wrong with it when I come back from my late report delivery! =]

回答3:

I was looking for the same solution. In the end, I am able to transfer the file upto 635MB without QDataStream.

I simply used below code.

for the client.

void MyClient::establishConnection(QString ip, quint16 port){

this->ip = ip;
this->port = port;

socket = new QTcpSocket();
socket->connectToHost(ip, port);

socket->waitForConnected(3000);
QFile file("D:/dummy.txt");   //file path      
file.open(QIODevice::ReadOnly);
QByteArray q = file.readAll();
socket->write(q);
}

for the server

void MyThread::readyRead(){


QByteArray line = socket->readAll();

QFile target;
target.setFileName("D:/new1.txt");


if (!target.open(QIODevice::WriteOnly | QIODevice::Append)) {
    qDebug() << "Can't open file for written";
    return;
}
target.write(line);

target.close();

qDebug() << "file size: " << target.size();

qDebug() << "Finished!";


}

Now, My Question is what will be the effect if I use QDataStream?

来源：https://stackoverflow.com/questions/30288385/how-to-send-a-file-in-qt

标签

c++

client

server