<![CDATA[Wanted to connect to PLC through ethernet but its not getting connected giving error device not open]]>Re: Qt gui C++ to read other controllers memory location through ethernet tcp/ip address
Wanted to connect to PLC through ethernet in Qt but its not getting connected giving error device not open.
but when connected through other means like using hercules the plc gets connected.

giving error :
QIODevice::write (QTcpSocket): device not open

program:

***clientnetworksocket=new QTcpSocket(this);
clientnetworksocket->connectToHost(QHostAddress("192.168.5.239"),5102,QIODevice::ReadWrite);
if (clientnetworksocket->waitForConnected(2000))
{
ui->label_status->setText("Connected to Server");

 }
 else
 {
     ui->label_status->setText("Server Offline");
   clientnetworksocket->disconnectFromHost();
   clientnetworksocket->close();
 }


 connect(timer, SIGNAL(timeout()), this, SLOT(monitorLoop()));
 timer->start(500);

 connect(clientnetworksocket,SIGNAL(readyRead()),this, SLOT(serialDataReceived()));

connect(clientnetworksocket,SIGNAL(disconnected()),this,SLOT(lineStatus()));***

]]>https://forum.qt.io/topic/127553/wanted-to-connect-to-plc-through-ethernet-but-its-not-getting-connected-giving-error-device-not-openRSS for NodeSat, 18 Apr 2026 00:40:16 GMTMon, 14 Jun 2021 11:53:17 GMT60<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Wed, 16 Jun 2021 06:25:18 GMT]]>@mganesh Is the IP correct? Is the port correct? Did you try to disable the firewall?
Also, you know that QTcpSocket provides functionality to get information about occurred errors? Why don't you use it?
So please check what https://doc.qt.io/qt-5/qabstractsocket.html#error and https://doc.qt.io/qt-5/qiodevice.html#errorString tell you after connection timeout...

]]>https://forum.qt.io/post/665380https://forum.qt.io/post/665380Wed, 16 Jun 2021 06:25:18 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Wed, 16 Jun 2021 06:20:52 GMT]]>no ..plz help to to connect to PLC

]]>https://forum.qt.io/post/665377https://forum.qt.io/post/665377Wed, 16 Jun 2021 06:20:52 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Mon, 14 Jun 2021 12:20:57 GMT]]>@mganesh So, did the connection succeed?

]]>https://forum.qt.io/post/664943https://forum.qt.io/post/664943Mon, 14 Jun 2021 12:20:57 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Mon, 14 Jun 2021 12:17:36 GMT]]>part of program:

***QByteArray data_to_transmit = QByteArray::fromHex(networkmonitorCommand);

    qDebug()<<networkmonitorCommand;

        clientnetworksocket->write(data_to_transmit);
         clientnetworksocket->flush();***
]]>https://forum.qt.io/post/664942https://forum.qt.io/post/664942Mon, 14 Jun 2021 12:17:36 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Mon, 14 Jun 2021 12:10:53 GMT]]>@mganesh said in Wanted to connect to PLC through ethernet but its not getting connected giving error device not open:

QIODevice::write (QTcpSocket): device not open

Where do you got this error?
On you code extract, there is not write.

]]>https://forum.qt.io/post/664940https://forum.qt.io/post/664940Mon, 14 Jun 2021 12:10:53 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Mon, 14 Jun 2021 12:07:15 GMT]]>removed whats next then also giving same error.

]]>https://forum.qt.io/post/664939https://forum.qt.io/post/664939Mon, 14 Jun 2021 12:07:15 GMT<![CDATA[Reply to Wanted to connect to PLC through ethernet but its not getting connected giving error device not open on Mon, 14 Jun 2021 11:58:53 GMT]]>@mganesh said in Wanted to connect to PLC through ethernet but its not getting connected giving error device not open:

clientnetworksocket->disconnectFromHost();

There is no need to disconnect if socket was not connected

]]>https://forum.qt.io/post/664938https://forum.qt.io/post/664938Mon, 14 Jun 2021 11:58:53 GMT