QMetaObject use in visual studio (or "asyncronous QSocketNotifier use")

[amdreallyfast]

I am using QtCreator 3.1.1, Qt library 4.8.5, and visual Studio 2013 Express.

For the last several hours, Qt has been kicking my butt. I am trying to perform asyncronous socket communication with a microcontroller, but QCoreApplication::exec() is blocking.

I could do something dirty like the following, but I'd rather learn to do it right:

#include <QtCore/QCoreApplication>
#include "my_socket_handler.h"
 
int main(int argc, char **argv)
{
   QCoreApplication app(argc, argv);
 
   while(1)
   {
      check_for_and_receive_incoming_data_over_sockets();
      app.processEvents();
   }
 
 
   return 0;
}

#include <QtCore/QCoreApplication>
#include "my_socket_handler.h"

int main(int argc, char **argv)
{
   QCoreApplication app(argc, argv);

   while(1)
   {
      check_for_and_receive_incoming_data_over_sockets();
      app.processEvents();
   }
   

   return 0;
}

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But that smells like foul code. I'd rather do it right with QSocketNotifier (or some other idea if you have one). Since I'm using visual studio, I'll use winsock. I got the following winsock code to work with QSocketNotifier in QtCreator:

#include <QCoreApplication>
#include <QSocketNotifier>
#include <QtDebug>
 
#include <WinSock2.h>
#include <WS2tcpip.h>
#pragma comment (lib, "Ws2_32.lib")
 
#include <iostream>
using std::cout;
using std::endl;
 
#define DEFAULT_PORT "5"
#define DEFAULT_HOST_ADDR "10.10.10.126"
#define DEFAULT_BUF_LEN 512
 
 
class RawSocketReader : public QObject
{
    Q_OBJECT
 
public slots:
    void doSomething(int socket)
    {
        char buff[DEFAULT_BUF_LEN];
        int length;
        while ((length = recv(socket, buff, DEFAULT_BUF_LEN, 0)) >= 0) {
            qDebug() << "Received" << length << "bytes";
        }
    }
};
 
// ??also, what the heck does this do and where does it live??
#include "main.moc"
 
int main(int argc, char *argv[]) {
    int app_ret_val = 0;
    QCoreApplication app(argc, argv);
 
    WSADATA wsa_data;
    struct addrinfo *result_ptr = 0;
    struct addrinfo hints;
    SOCKET my_socket = INVALID_SOCKET;
 
    int rx_byte_count = 0;
    char rx_buf[DEFAULT_BUF_LEN];
 
    // initialize WSA stuff
    WSAStartup(MAKEWORD(2, 2), &wsa_data);
 
    // set up the "hints" struct that will guide the search for
    // the host
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
 
    getaddrinfo("10.10.10.126", "5", &hints, &result_ptr);
    my_socket = socket(
                result_ptr->ai_family,
                result_ptr->ai_socktype,
                result_ptr->ai_protocol);
 
    connect(
                my_socket,
                result_ptr->ai_addr,
                (int)(result_ptr->ai_addrlen));
 
 
    QSocketNotifier notifier(my_socket, QSocketNotifier::Read);
    RawSocketReader reader;
    QObject::connect(
                & notifier, 
                SIGNAL(activated(int)), 
                &reader, 
                SLOT(doSomething(int)));
 
    app_ret_val = app.exec();
 
    closesocket(my_socket);
    my_socket = INVALID_SOCKET;
    freeaddrinfo(result_ptr);
    WSACleanup();
 
 
    return app_ret_val;
}

#include <QCoreApplication>
#include <QSocketNotifier>
#include <QtDebug>

#include <WinSock2.h>
#include <WS2tcpip.h>
#pragma comment (lib, "Ws2_32.lib")

#include <iostream>
using std::cout;
using std::endl;

#define DEFAULT_PORT "5"
#define DEFAULT_HOST_ADDR "10.10.10.126"
#define DEFAULT_BUF_LEN 512


class RawSocketReader : public QObject
{
    Q_OBJECT

public slots:
    void doSomething(int socket)
    {
        char buff[DEFAULT_BUF_LEN];
        int length;
        while ((length = recv(socket, buff, DEFAULT_BUF_LEN, 0)) >= 0) {
            qDebug() << "Received" << length << "bytes";
        }
    }
};

// ??also, what the heck does this do and where does it live??
#include "main.moc"

int main(int argc, char *argv[]) {
    int app_ret_val = 0;
    QCoreApplication app(argc, argv);

    WSADATA wsa_data;
    struct addrinfo *result_ptr = 0;
    struct addrinfo hints;
    SOCKET my_socket = INVALID_SOCKET;

    int rx_byte_count = 0;
    char rx_buf[DEFAULT_BUF_LEN];

    // initialize WSA stuff
    WSAStartup(MAKEWORD(2, 2), &wsa_data);

    // set up the "hints" struct that will guide the search for
    // the host
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    getaddrinfo("10.10.10.126", "5", &hints, &result_ptr);
    my_socket = socket(
                result_ptr->ai_family,
                result_ptr->ai_socktype,
                result_ptr->ai_protocol);

    connect(
                my_socket,
                result_ptr->ai_addr,
                (int)(result_ptr->ai_addrlen));


    QSocketNotifier notifier(my_socket, QSocketNotifier::Read);
    RawSocketReader reader;
    QObject::connect(
                & notifier, 
                SIGNAL(activated(int)), 
                &reader, 
                SLOT(doSomething(int)));
    
    app_ret_val = app.exec();

    closesocket(my_socket);
    my_socket = INVALID_SOCKET;
    freeaddrinfo(result_ptr);
    WSACleanup();


    return app_ret_val;
}

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But I can't get that "QObject::connect(...)" call to work in Visual Studio. The problem seems to stem from the SIGNAL and SLOT calls, which QtCreator can process, but Visual Studio can't (or at least, I haven't figured it out yet). They are supposed to supply QMetaMethod references to the "QObject::connect(...)" function, but they aren't. According to the compiler error, they are providing "const char *" arguments (the "SIGNAL" and "SLOT" #defines seem to merely return pointers to the method).

I think my solution lies in QMetaMethod, but I am having difficulty piecing together documentation from different Qt things just to figure out how to construct the thing, and I haven't yet figured out what .lib or .dll it lives in. Just about all the documentation about meta stuff and SIGNAL and SLOT seems to be written in the assumption that QtCreator is being used.


So I'm stuck. Help? I want to get asynchronous socket communication up and running within a Qt application.