ZMQ Python PUB/SUB works but not my C++ Subscriber with Python Publisher

I am using Ubuntu 18.04, Qt 5.12, and libzmq.so.5.1.5. I have 2 very simple Python 3.6 scripts, using pyzmq 18.0.1, one implements ZMQ PUB and one implements ZMQ SUB. These Python scripts work find and data is transmitted from one to the other on the localhost loopback network. I am trying to implement the subscriber in Qt 5.12, and the subscriber always blocks on receive when I send the same data using the same Python publisher script. I’ve pasted the complete code below – how I can I get ZMQ with Qt 5.12 to actually received data? Thanks.

The output of my C++ app looks successful:

"Server IP Address determined to be: 127.0.0.1"
"Connecting to: tcp://127.0.0.1:5555"
"Attempted Connect: 0"
"SetSockOpt: 0"
"GetSockOpt: 0"
Done setting up socket
Waiting

Python 3 PUB:

#!/usr/bin/python3

import time
import zmq
context = zmq.Context()
socket = context.socket(zmq.PUB)
socket.bind("tcp://127.0.0.1:5555")

# Allow clients to connect before sending data
time.sleep(3)
while True:
    socket.send_pyobj({1:[1,2,3]})
    time.sleep(1)

Python 3 SUB:

#!/usr/bin/python3

import zmq
context = zmq.Context()
socket = context.socket(zmq.SUB)
# We can connect to several endpoints if we desire, and receive from all.
socket.connect("tcp://127.0.0.1:5555")

# We must declare the socket as of type SUBSCRIBER, and pass a prefix filter.
# Here, the filter is the empty string, which means we receive all messages.
# We may subscribe to several filters, thus receiving from all.
socket.setsockopt(zmq.SUBSCRIBE, b'')

while True:
    message = socket.recv_pyobj()
    print(message.get(1)[2])

Qt 5.12 Subscriber Code:

#include <QCoreApplication>
   
// Std includes
#include <stdio.h>
#include <unistd.h>
#include <assert.h>

// Qt
#include <QDebug>
#include <QFile>

// ZeroMQ Includes
#include <zmq.h>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
   
    //QString m_ServerIP = QString("*");
    QString m_ServerIP = QString("127.0.0.1");
    QString m_ServerPort = QString("5555");

    qDebug() << QString("Server IP Address determined to be: %1").arg(m_ServerIP);

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

        const char *filter = std::string("").c_str();
        QString ipAndPort = QString("tcp://%1:%2").arg(m_ServerIP).arg(m_ServerPort);

        qDebug() << QString("Connecting to: %1").arg(ipAndPort);

        rc = zmq_connect(m_Subscriber, ipAndPort.toStdString().c_str());

        qDebug() << QString("Attempted Connect: %1").arg(rc);

        rc = zmq_setsockopt(m_Subscriber, ZMQ_SUBSCRIBE,filter, strlen (filter));

        qDebug() << QString("SetSockOpt: %1").arg(rc);

        size_t fd_size = sizeof(fd);

        rc = zmq_getsockopt(m_Subscriber,ZMQ_FD,&fd,&fd_size);

        qDebug() << QString("GetSockOpt: %1").arg(rc);

    }
    while ( rc < 0 );

    qDebug() << "Done setting up socket";

    while ( true) {

        zmq_msg_t message;
        zmq_msg_init(&message);
        qDebug() << "Waiting";
        zmq_recvmsg(m_Subscriber, &message, 0);
        size_t size = zmq_msg_size (&message);

        qDebug() << 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);

            qDebug() << QString("Debug RX Frame Size: %1").arg(frame.size());

            QFile output("/tmp/abcd.jpeg");
            if ( output.open(QIODevice::WriteOnly) ) {
                output.write(frame);
                output.close();
            }

        }

    }

    return a.exec();
}