Another threads problem

Damian7546

Hi,
I have simple modbus communication in new thread, smoe like below:

void qmodbus::run(){
.
.
.
//define write command function
    auto send_wr_cmd= [&](const quint16 cmd){
            wr_cmd.setValue(1,cmd);
            reply_wr_cmd=mc.sendWriteRequest(wr_cmd,1); //new Request modbus adress 1
            if(reply_wr_cmd->isFinished()){
                delete reply_wr_cmd;
            }else{
                connect(wr_reply,&QModbusReply::finished,wr_rpl_redy); //set callback function when reply ready.  call[0]
            }
      
    };

.
.
.

connect(this, &qmodbus::write_command, send_wr_cmd);


 if (!mc.connectDevice()){
        exit();
        return;
    }
    exec(); //qt event loop
}

Where I try write to modbus form outside thread by connect signals:

connect(this, &Inverter::write_command, mbus, &qmodbus::write_command);

and I have a problem:
QSocketNotifier: Socket notifiers cannot be enabled or disabled from another thread
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QModbusTcpClient(0x4b0f854), parent's thread is qmodbus(0xbf4680), current thread is QThread(0xbbb2c8)

but it works the other way round:

 connect(mbus, &qmodbus::updateData, this, &Inverter::updateData);

why ?

Christian Ehrlicher

@Damian7546 said in Another threads problem:

why ?

Because mc is not in the correct thread - simply calling an object in another thread without properly moving (or directly creating) it there will not work.
Please read the docs: https://doc.qt.io/qt-6/thread-basics.html

There is no need to use a thread here at all - use signals and slots from QModbusReply: https://doc.qt.io/qt-6/qmodbusreply.html