linux - ZeroMQ with Qt 5.12 QSocketNotifier 只触发一次

Question

在 Ubuntu 16.04 机器上，我使用 Python3 和 pyzmq 通过 ZeroMQ PUB/SUB 套接字将 base64 结尾的 JPEG 发送到 Qt5 应用程序。 Qt5 应用程序使用 QSocketNotifier 来监视 ZMQ 套接字，并且应该在套接字“激活”并读取更多数据时触发。在我的例子中，数据在 Qt5 端被完全接收并且 JPEG 看起来没问题——但是，套接字通知程序只触发一次，即使 Python 发布者一直在发送数据。如果我使用 ctrl-C 退出 Python 应用程序，则会在 Qt5 应用程序端触发套接字通知程序激活槽的另一个实例。我希望每次从 Python 发送 ZMQ 消息时触发插槽。我在下面附上了 Python 和 Qt5 的整个应用程序。我怎样才能使它工作？

-------- Header File ------

#ifndef SOCKETRECEIVER_H
#define SOCKETRECEIVER_H

#include <QObject>

// Debug
#include <QDebug>
#include <QDataStream>
#include <QFile>
#include <unistd.h>

// User ZeroMQ Sockets
#include <QSocketNotifier>

// ZeroMQ Includes
#include <zmq.h>

// Debug prints
static void AppDebug(QString message) {
    qDebug() << Q_FUNC_INFO << message;
}

class SocketReceiver : public QObject
{

    Q_OBJECT

public:

    explicit SocketReceiver(QObject *parent = nullptr);
    ~SocketReceiver();

private slots:

    void readZMQData();

private:

    QSocketNotifier *m_SocketNotifier;
    void *m_Context;
    void *m_Subscriber;
    long long int m_RxFrameCounter;
    bool m_DidRXFrame;

signals:

public slots:
};

#endif // SOCKETRECEIVER_H

-------- CCP File ------

#include "socketreceiver.h"

SocketReceiver::SocketReceiver(QObject *parent) : QObject(parent) ,  m_SocketNotifier(nullptr) , m_Context(nullptr) , m_Subscriber(nullptr) , m_RxFrameCounter(0) , m_DidRXFrame(false)
{

    /***** ZMQ *****/

    int major, minor, patch;
    zmq_version (&major, &minor, &patch);

    m_Context = zmq_ctx_new();
    m_Subscriber = zmq_socket (m_Context, ZMQ_SUB);
    int rc = -1;
    unsigned int fd = 0;
    do {

    const char *filter = std::string("").c_str();
    rc = zmq_connect (m_Subscriber, "tcp://localhost:5556");
    rc = zmq_setsockopt (m_Subscriber, ZMQ_SUBSCRIBE,filter, strlen (filter));
    size_t fd_size = sizeof(fd);
    rc = zmq_getsockopt(m_Subscriber,ZMQ_FD,&fd,&fd_size);

    m_SocketNotifier = new QSocketNotifier(fd, QSocketNotifier::Read, this);
    connect(m_SocketNotifier, SIGNAL(activated(int)), this, SLOT(readZMQData()), Qt::DirectConnection);

    }
    while ( rc < 0 );

    AppDebug("Done setting up");

}

SocketReceiver::~SocketReceiver()
{

    zmq_close (this->m_Subscriber);
    zmq_ctx_destroy (this->m_Context);

}

void SocketReceiver::readZMQData()
{

    m_SocketNotifier->setEnabled(false);

    AppDebug("Waiting for next frame...");

    QByteArray newFrame;

    int events = 0;
    std::size_t eventsSize = sizeof(events);
    zmq_getsockopt(m_Subscriber,ZMQ_EVENTS, &events, &eventsSize);
    if(events & ZMQ_POLLIN){

    AppDebug("Read Data...");

    // Receive data from socket
    zmq_msg_t message;
    zmq_msg_init(&message);
    zmq_recvmsg(m_Subscriber, &message, 0);
    size_t size = zmq_msg_size (&message);
    AppDebug(QString("Message Size: %1").arg(size));
    char *string = static_cast<char*>(malloc(size + 1));
    memcpy (string, zmq_msg_data(&message), size);
    zmq_msg_close (&message);
    string [size] = 0;

    if ( string != nullptr ) {

        QByteArray newDecodedData = QByteArray::fromBase64(QByteArray(string));
        newFrame.append(newDecodedData);
        free(string);

        if ( !m_DidRXFrame ) {
            m_DidRXFrame = true;
        }

        if ( m_RxFrameCounter == 0 && m_DidRXFrame ) {

            AppDebug(QString("Debug RX Frame Size: %1").arg(newFrame.size()));
            QFile output("/tmp/abcd.jpeg");
            if ( output.open(QIODevice::WriteOnly) ) {
                output.write(newFrame);
                output.close();
                //sleep(86400);
            }

        }

        m_RxFrameCounter++;

    }

    }

    AppDebug("Setting enabled true...");

    m_SocketNotifier->setEnabled(true);

}

-------- Python 脚本------------

#!/usr/bin/python3

import zmq
import random
import sys
import time
import base64

context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://*:5556")

time.sleep(1)
while True:
    f = open("test.jpg",'rb')
    bytes = bytearray(f.read())
    print("Encoded Data Length: %s"%(len(bytes)))
    strng = base64.b64encode(bytes)
    print("Encoded Data Length: %s"%(len(strng)))
    socket.send(strng)
    f.close()
    time.sleep(1)

Answer 1

你必须使用一段时间，因为在读取数据时你可以得到另一个数据:

int SocketReceiver::events(){
    int events = 0;
    std::size_t eventsSize = sizeof(events);
    zmq_getsockopt(m_Subscriber,ZMQ_EVENTS, &events, &eventsSize);
    return events;
}

void SocketReceiver::readZMQData()
{
    m_SocketNotifier->setEnabled(false);
    while (events() & ZMQ_POLLIN) {
        zmq_msg_t message;
        zmq_msg_init(&message);
        zmq_recvmsg(m_Subscriber, &message, 0);
        size_t size = zmq_msg_size (&message);
        AppDebug(QString("Message Size: %1").arg(size));
        char *string = static_cast<char*>(malloc(size + 1));
        memcpy (string, zmq_msg_data(&message), size);
        zmq_msg_close (&message);
        string [size] = 0;
        if (string) {
            QByteArray frame = QByteArray::fromBase64(QByteArray(string));
            free(string);
            AppDebug(QString("Debug RX Frame Size: %1").arg(frame.size()));
            QFile output("/tmp/abcd.jpeg");
            if ( output.open(QIODevice::WriteOnly) ) {
                output.write(frame);
                output.close();
            }
        }
    }
    m_SocketNotifier->setEnabled(true);
}