QSerial without QThreads

Question

I create a "server" lib with a Qt GUI.

I don't and can't use QThreads because this is supposed to be as independent from Qt as possible, and because I have other threads already working like a Ethernet part.

The thread ExternalRs232Thread() is lauched by the public function RunExternalRs232()

RunExternalRs232() opens the serial port, returns -1 if can't open serial, and if is ok runs the function ExternalRs232Thread() in a detached thread.

Initially, I have tried to run this with Serialib, but this never works properly with the Qt project. So I decided to give QSerialPort a try like this:

Server.h

#ifndef SERVER_H
#define SERVER_H

#include <iostream>
#include <winsock2.h>
#include <windows.h>
#include <thread>
#include <unordered_map>
#include <unordered_set>
#include <sstream>
#include <time.h>
#include <chrono>
#include <mutex>

#include <QObject>

#include "libs/json.hpp"
#include <QtSerialPort>

#include "hdlccsvparser.h"

using namespace std;
using json = nlohmann::json;
using std::chrono::milliseconds;
using std::chrono::duration_cast;
using std::chrono::seconds;
using std::chrono::system_clock;

struct Contact {
    int port;    //udp port of te contact
    time_t time; //last communication date ( is still active ? )
};

class Server : public QObject
{

Q_OBJECT

public:
    Server();
    virtual ~Server();

    [...]

    //return 0 if sucess , 1 port is not usabe, 2 port already in use
    int RunExternalRs232(string PortCom, unsigned int baudrate);
    int StopExternalRs232(string PortCom);

    [...]

    //clean exit
    void ExitServer();


signals:
    [...]

private:
    [...]

    // External ThreadS and exiting loop of threadS in set (if key d'ont exist anymore, exit loop)
    mutex mtxExternalRs232;
    unordered_set<string> ExternalRs232PortActiveList;
    void ExternalRs232Thread(QSerialPort* Rs232Connection, string port);

    [...]
};

#endif // SERVER_H

Server.cpp

#include "Server/Server.h"
#include <winsock2.h>

/* Public Part*/

[...]

int Server::RunExternalRs232(string PortCom, unsigned int baudrate){
    //PortCom = (char *)"COM1";
    //baudrate = 9600;

    QSerialPort Rs232Connection;

    // Connection to serial port
    // COMxx
    Rs232Connection.setPortName(QString::fromStdString(PortCom));
    Rs232Connection.setBaudRate(baudrate);

    Rs232Connection.setDataBits(QSerialPort::Data8);
    Rs232Connection.setParity(QSerialPort::NoParity);
    Rs232Connection.setStopBits(QSerialPort::OneStop);
    Rs232Connection.setFlowControl(QSerialPort::NoFlowControl);

    int i = Rs232Connection.open(QIODevice::ReadWrite);


    // If connection fails, errorOpening != 1
    if(i != 1){
        return i;
    }

    mtxExternalRs232.lock();
    ExternalRs232PortActiveList.insert(PortCom);
    mtxExternalRs232.unlock();

    cout << "External Rs232 starting on " << PortCom << endl;
    stringstream sstmp;
    sstmp << PortCom;
    emit LogMessage(QString::fromStdString("External Rs232 starting on " + sstmp.str()),0);

    std::thread thServer(&Server::ExternalRs232Thread,this,&Rs232Connection,PortCom);
    thServer.detach();
    return 0;

}

int Server::StopExternalRs232(string PortCom){

    PortCom = "COM1";

    mtxExternalRs232.lock();
    /*
    if(ExternalRs232PortActiveList.count(PortCom) != 1){ //???
        //port not in use

        cerr << "close Failed Rs232 " << PortCom << endl;
        mtxExternalRs232.unlock();
        return 1;
    }*/

    cout << "close External Rs232 " << PortCom << endl;
    ExternalRs232PortActiveList.erase(PortCom);
    mtxExternalRs232.unlock();
    return 0;

    mtxExternalRs232.lock();
    cout << ExternalRs232PortActiveList.count(PortCom) << " here " << endl;
    mtxExternalRs232.unlock();
}

[...]

/* Private Part */

/*   Thread part */

[...]

void Server::ExternalRs232Thread(QSerialPort * Rs232Connection, string port){

    //char/binary read on rs232
    char tmp;

    //if rs232 has data
    bool res = false;

    stringstream message;
    Rs232Connection->write("H");

    mtxExternalRs232.lock();
    int iscount = ExternalRs232PortActiveList.count(port);
    mtxExternalRs232.unlock();

    while(iscount == 1){
        res = false;


        if(!Rs232Connection->waitForReadyRead(300)){
            //no data skipp
        } else {
            QByteArray datas = Rs232Connection->readAll();

            QTextCodec *codec = QTextCodec::codecForName("UTF-8");
            string tmp = codec->toUnicode(datas).toStdString();

            cout << tmp << endl;
        }

        mtxExternalRs232.lock();
        iscount = ExternalRs232PortActiveList.count(port);
        mtxExternalRs232.unlock();

    }
    Rs232Connection->flush();
    Rs232Connection->close();
}

[...]

/* functions part */

[...]

Server::Server(){
    //init winsock
    if(WSAStartup(MAKEWORD(2,2),&wsa) != 0){
        cerr << "Could not init winsock2 : " << WSAGetLastError();
    }

    //creating a socket
    if((s = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET){
        cerr << "Could not create a socket : " << WSAGetLastError();
    }
}

Server::~Server(){
    //dtor
}

at the end, I get

QObject::startTimer: Timers can only be used with threads started with QThreads

So how is possible to run Serial Rs232 without using QThreads?